Method and apparatus for transmitting/receiving wireless signal in wireless communication system

ABSTRACT

The present invention relates to a wireless communication system and, more particularly, to a method and an apparatus therefor, the method comprising the steps of: identifying a minimum storing area per data in a HARQ buffer on the basis of a TTI length; storing data for transmission of a wireless signal in the HARQ buffer on the basis of the minimum storing area per data; and transmitting the data in the HARQ buffer during a first TTI, wherein, when the data is retransmitted data, the minimum storing area per data is based on the length of a second TTI used for initial transmission of the data, and the length of the second TTI is different from the length of the first TTI.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/895,597, filed on Jun. 8, 2020, which is a continuation of U.S.application Ser. No. 16/532,090, filed on Aug. 5, 2019, now U.S. Pat.No. 10,680,761, which is a continuation of International Application No.PCT/KR2018/001515, filed on Feb. 5, 2018, which claims the benefit ofU.S. Provisional Application No. 62/593,273, filed on Dec. 1, 2017, U.S.Provisional Application No. 62/586,876, filed on Nov. 15, 2017, U.S.Provisional Application No. 62/566,338, filed on Sep. 30, 2017, U.S.Provisional Application No. 62/555,705, filed on Sep. 8, 2017, U.S.Provisional Application No. 62/525,172, filed on Jun. 26, 2017, U.S.Provisional Application No. 62/520,563, filed on Jun. 16, 2017, U.S.Provisional Application No. 62/501,052, filed on May 3, 2017, U.S.Provisional Application No. 62/481,043, filed on Apr. 3, 2017, U.S.Provisional Application No. 62/469,548, filed on Mar. 10, 2017, and U.S.Provisional Application No. 62/454,893, filed on Feb. 5, 2017. Thedisclosures of the prior applications are incorporated by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to a wireless communication system, andmore particularly, to a method and apparatus for transmitting/receivinga wireless signal. The wireless communication system includes a CA-based(Carrier Aggregation-based) wireless communication system.

BACKGROUND

Wireless communication systems have been widely deployed to providevarious types of communication services including voice and dataservices. In general, a wireless communication system is a multipleaccess system that supports communication among multiple users bysharing available system resources (e.g. bandwidth, transmit power,etc.) among the multiple users. The multiple access system may adopt amultiple access scheme such as code division multiple access (CDMA),frequency division multiple access (FDMA), time division multiple access(TDMA), orthogonal frequency division multiple access (OFDMA), or singlecarrier frequency division multiple access (SC-FDMA).

SUMMARY

It is an object of the present invention to provide a method andapparatus for efficiently performing operations of transmission andreception of a wireless signal.

Technical tasks obtainable from the present invention are not limited bythe above-mentioned technical task. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

In one aspect of the present invention, provided herein is a method fortransmitting a wireless signal by a communication device in a wirelesscommunication system, the method including checking a minimum storagespace per data in a Hybrid Automatic Repeat and reQuest (Hybrid ARQ,HARQ) buffer based on a transmission time interval (TTI) length, storingdata for transmission of the wireless signal in the HARQ buffer based onthe minimum storage space per data, and transmitting the data in theHARQ buffer for a first TTI, wherein, when the data is retransmitteddata, the minimum storage space per data is based on a length of asecond TTI used for initial transmission of the data, the length of thesecond TTI being different from a length of the first TTI.

In another aspect of the present invention, provided herein is acommunication device used in a wireless communication system, includingan radio frequency (RF) module, and a processor, wherein the processoris configured to check a minimum storage space per data in a Hybrid ARQ(HARQ) buffer based on a transmission time interval (TTI) length, storedata for transmission of the wireless signal in the HARQ buffer based onthe minimum storage space per data, and transmit the data in the HARQbuffer for a first TTI, wherein, when the data is retransmitted data,the minimum storage space per data is based on a length of a second TTIused for initial transmission of the data, the length of the second TTIbeing different from a length of the first TTI.

The checking of the minimum storage space per data may be performed bydividing an entire space of the HARQ buffer by the number of HARQprocesses corresponding to the TTI length.

The checking of the minimum storage space per data may be performed bydividing an entire space of the HARQ buffer into a plurality of sub-HARQbuffers according to the number of TTI lengths and then dividing each ofthe sub-HARQ buffers by the number of HARQ processes corresponding to acorresponding TTI length.

When the length of the first TTI is greater than the length of thesecond TTI, the minimum storage space per data based on the length ofthe first TTI may be checked by dividing an entire space of the HARQbuffer by the number of HARQ processes corresponding to the length ofthe first TTI, and the minimum storage space per data based on thelength of the second TTI may be checked by dividing a partial space ofthe HARQ buffer by the number of HARQ processes corresponding to thelength of the second TTI.

The communication device may have a plurality of component carrier (CCs)for different radio access technologies (RATs) aggregated, and a size ofthe HARQ buffer may be determined by the following equations accordingto the RATs used for transmission of the wireless signal:

-   -   Buffer size for RAT1: S*A*(N1/N); and    -   Buffer size for RAT2: S*B*(N2/N).

Herein, S denotes a total size of the HARQ buffer in the communicationdevice, A and B denote coefficients indicative of a ratio of the buffersizes for RAT1 and RAT2, N1 denotes the number of CCs configured forRAT1, N2 denotes the number of CCs configured for RAT2, and N denotes asum of N1 and N2.

A size of the TTI length may be given in the following order accordingto a service type: Ultra-Reliable and Low Latency Communications(URLLC)<enhanced Mobile Broadband (eMBB)<massive Machine TypeCommunications (mMTC).

The wireless communication system may include a Third Generation ProjectPartnership Long Term Evolution (3GPP LTE)-based wireless communicationsystem, wherein the TTI length may be a multiple of a subframe or slot.

According to embodiments of the present invention, wireless signaltransmission and reception can be efficiently performed in a wirelesscommunication system.

Effects obtainable from the present invention are non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 illustrates physical channels used in a 3GPP LTE(-A) system,which is an example of a wireless communication system, and a typicalsignal transmission method using the same.

FIGS. 2A and 2B illustrate a radio frame structure.

FIG. 3 illustrates a resource grid of a downlink slot.

FIG. 4 illustrates a downlink subframe structure.

FIG. 5 illustrates an example of Enhanced Physical Downlink ControlChannel (EPDCCH).

FIG. 6 illustrates the structure of an uplink subframe used in LTE(-A).

FIG. 7 illustrates UL HARQ (Uplink Hybrid Automatic Repeat reQuest)operation.

FIGS. 8 and 9 illustrate TDD UL ACK/NACK (UplinkAcknowledgement/Negative Acknowledgement) transmission timing in asingle cell case.

FIGS. 10 and 11 illustrate TDD PUSCH (Physical Uplink Shared Channel)transmission timing in a single cell case.

FIGS. 12 and 13 illustrate TDD DL ACK/NACK transmission timing in asingle cell case.

FIG. 14 illustrates a TDD HARQ (Hybrid Automatic Repeat request) processin a single cell situation.

FIG. 15 illustrates a carrier aggregation (CA)-based wirelesscommunication system.

FIG. 16 illustrates cross-carrier scheduling.

FIG. 17 illustrates a structure of a self-contained subframe.

FIGS. 18 to 22 illustrate a signal transmission procedure according tothe present invention.

FIG. 23 illustrates a base station and user equipment applicable to anembodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention are applicable to a variety ofwireless access technologies such as code division multiple access(CDMA), frequency division multiple access (FDMA), time divisionmultiple access (TDMA), orthogonal frequency division multiple access(OFDMA), and single carrier frequency division multiple access(SC-FDMA). CDMA can be implemented as a radio technology such asUniversal Terrestrial Radio Access (UTRA) or CDMA2000. TDMA can beimplemented as a radio technology such as Global System for Mobilecommunications (GSM)/General Packet Radio Service (GPRS)/Enhanced DataRates for GSM Evolution (EDGE). OFDMA can be implemented as a radiotechnology such as Institute of Electrical and Electronics Engineers(IEEE) 802.11 (Wireless Fidelity (Wi-Fi)), IEEE 802.16 (Worldwideinteroperability for Microwave Access (WiMAX)), IEEE 802.20, and EvolvedUTRA (E-UTRA). UTRA is a part of Universal Mobile TelecommunicationsSystem (UMTS). 3rd Generation Partnership Project (3GPP) Long TermEvolution (LTE) is a part of Evolved UMTS (E-UMTS) using E-UTRA, andLTE-Advanced (LTE-A) is a evolved version of 3GPP LTE. While thefollowing description is given, centering on 3GPP LTE/LTE-A for clarity,this is purely exemplary and thus should not be construed as limitingthe present invention.

In a wireless communication system, a UE receives information from abase station (BS) through downlink (DL), and transmits information tothe BS through uplink (UL). The information transmitted and received bythe BS and the UE includes data and various kinds of controlinformation, and there are various physical channels according to thetypes/uses of the information transmitted/received by the BS and the UE.

FIG. 1 illustrates physical channels used in 3GPP LTE(-A) and a signaltransmission method using the same.

When powered on or when a UE initially enters a cell, the UE performsinitial cell search involving synchronization with a BS in step S101.For initial cell search, the UE synchronizes with the BS and acquireinformation such as a cell Identifier (ID) by receiving a primarysynchronization channel (P-SCH) and a secondary synchronization channel(S-SCH) from the BS. Then the UE may receive broadcast information fromthe cell on a physical broadcast channel (PBCH). In the meantime, the UEmay check a downlink channel status by receiving a downlink referencesignal (DL RS) during initial cell search.

After initial cell search, the UE may acquire more specific systeminformation by receiving a physical downlink control channel (PDCCH) andreceiving a physical downlink shared channel (PDSCH) based oninformation of the PDCCH in step S102.

The UE may perform a random access procedure to access the BS in stepsS103 to S106. For random access, the UE may transmit a preamble to theBS on a physical random access channel (PRACH) (S103) and receive aresponse message for preamble on a PDCCH and a PDSCH corresponding tothe PDCCH (S104). In the case of contention-based random access, the UEmay perform a contention resolution procedure by further transmittingthe PRACH (S105) and receiving a PDCCH and a PDSCH corresponding to thePDCCH (S106).

After the foregoing procedure, the UE may receive a PDCCH/PDSCH (S107)and transmit a physical uplink shared channel (PUSCH)/physical uplinkcontrol channel (PUCCH) (S108), as a general downlink/uplink signaltransmission procedure. Control information transmitted from the UE tothe BS is referred to as uplink control information (UCI). The UCIincludes hybrid automatic repeat and requestacknowledgement/negative-acknowledgement (HARQ-ACK/NACK), schedulingrequest (SR), channel state information (CSI), etc. The CSI includes achannel quality indicator (CQI), a precoding matrix indicator (PMI), arank indicator (RI), etc. While the UCI is transmitted on a PUCCH ingeneral, the UCI may be transmitted on a PUSCH when control informationand traffic data need to be simultaneously transmitted. In addition, theUCI may be aperiodically transmitted through a PUSCH according torequest/command of a network.

FIGS. 2A and 2B illustrate a radio frame structure. Uplink/downlink datapacket transmission is performed on a subframe-by-subframe basis. Asubframe is defined as a predetermined time interval including aplurality of symbols. 3GPP LTE supports a type-1 radio frame structureapplicable to frequency division duplex (FDD) and a type-2 radio framestructure applicable to time division duplex (TDD).

FIG. 2A illustrates a type-1 radio frame structure. A downlink subframeincludes 10 subframes each of which includes 2 slots in the time domain.A time for transmitting a subframe is defined as a transmission timeinterval (TTI). For example, each subframe has a duration of 1 ms andeach slot has a duration of 0.5 ms. A slot includes a plurality of OFDMsymbols in the time domain and includes a plurality of resource blocks(RBs) in the frequency domain. Since downlink uses OFDM in 3GPP LTE, anOFDM symbol represents a symbol period. The OFDM symbol may be called anSC-FDMA symbol or symbol period. An RB as a resource allocation unit mayinclude a plurality of consecutive subcarriers in one slot.

The number of OFDM symbols included in one slot may depend on cyclicprefix (CP) configuration. CPs include an extended CP and a normal CP.When an OFDM symbol is configured with the normal CP, for example, thenumber of OFDM symbols included in one slot may be 7. When an OFDMsymbol is configured with the extended CP, the length of one OFDM symbolincreases, and thus the number of OFDM symbols included in one slot issmaller than that in case of the normal CP. In case of the extended CP,the number of OFDM symbols allocated to one slot may be 6. When achannel state is unstable, such as a case in which a UE moves at a highspeed, the extended CP can be used to reduce inter-symbol interference.

When the normal CP is used, one subframe includes 14 OFDM symbols sinceone slot has 7 OFDM symbols. The first three OFDM symbols at most ineach subframe can be allocated to a PDCCH and the remaining OFDM symbolscan be allocated to a PDSCH.

FIG. 2B illustrates a type-2 radio frame structure. The type-2 radioframe includes 2 half frames. Each half frame includes 4(5) normalsubframes and 10 special subframes. The normal subframes are used foruplink or downlink according to UL-DL configuration. A subframe iscomposed of 2 slots.

Table 1 shows subframe configurations in a radio frame according toUL-DL configurations.

TABLE 1 Downlink- Uplink- to-Uplink downlink Switch point Subframenumber configuration periodicity 0 1 2 3 4 5 6 7 8 9 0  5 ms D S U U U DS U U U 1  5 ms D S U U D D S U U D 2  5 ms D S U D D D S U D D 3 10 msD S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D DD D 6  5 ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframeand S denotes a special subframe. The special subframe includes DwPTS(Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS (Uplink PilotTimeSlot). DwPTS is used for initial cell search, synchronization orchannel estimation in a UE and UpPTS is used for channel estimation in aBS and uplink transmission synchronization in a UE. The GP eliminates ULinterference caused by multi-path delay of a DL signal between a UL anda DL.

The radio frame structure is merely exemplary and the number ofsubframes included in the radio frame, the number of slots included in asubframe, and the number of symbols included in a slot can be vary.

FIG. 3 illustrates a resource grid of a downlink slot.

Referring to FIG. 3 , a downlink slot includes a plurality of OFDMsymbols in the time domain. While one downlink slot may include 7 OFDMsymbols and one resource block (RB) may include 12 subcarriers in thefrequency domain in the figure, the present invention is not limitedthereto. Each element on the resource grid is referred to as a resourceelement (RE). One RB includes 12×7 REs. The number NRB of RBs includedin the downlink slot depends on a downlink transmit bandwidth. Thestructure of an uplink slot may be same as that of the downlink slot.

FIG. 4 illustrates a downlink subframe structure.

Referring to FIG. 4 , a maximum of three (four) OFDM symbols located ina front portion of a first slot within a subframe correspond to acontrol region to which a control channel is allocated. The remainingOFDM symbols correspond to a data region to which a physical downlinkshared chancel (PDSCH) is allocated. A basic resource unit of the dataregion is an RB. Examples of downlink control channels used in LTEinclude a physical control format indicator channel (PCFICH), a physicaldownlink control channel (PDCCH), a physical hybrid ARQ indicatorchannel (PHICH), etc. The PCFICH is transmitted at a first OFDM symbolof a subframe and carries information regarding the number of OFDMsymbols used for transmission of control channels within the subframe.The PHICH is a response of uplink transmission and carries an HARQacknowledgment (ACK)/negative-acknowledgment (NACK) signal. Controlinformation transmitted through the PDCCH is referred to as downlinkcontrol information (DCI). The DCI includes uplink or downlinkscheduling information or an uplink transmit power control command foran arbitrary UE group.

Control information transmitted through the PDCCH is referred to asdownlink control information (DCI). Formats 0, 3, 3A and 4 for uplinkand formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B and 2C for downlink are definedas DCI formats. Information field type, the number of informationfields, the number of bits of each information field, etc. depend on DICformat. For example, the DCI formats selectively include informationsuch as hopping flag, RB assignment, MCS (Modulation Coding Scheme), RV(Redundancy Version), NDI (New Data Indicator), TPC (Transmit PowerControl), HARQ process number, PMI (Precoding Matrix Indicator)confirmation as necessary. Accordingly, the size of control informationmatched to a DCI format depends on the DCI format. A arbitrary DCIformat may be used to transmit two or more types of control information.For example, DIC formats 0/1A is used to carry DCI format 0 or DICformat 1, which are discriminated from each other using a flag field.

A PDCCH may carry a transport format and a resource allocation of adownlink shared channel (DL-SCH), resource allocation information of anuplink shared channel (UL-SCH), paging information on a paging channel(PCH), system information on the DL-SCH, information on resourceallocation of an upper-layer control message such as a random accessresponse transmitted on the PDSCH, a set of Tx power control commands onindividual UEs within an arbitrary UE group, a Tx power control command,information on activation of a voice over IP (VoIP), etc. A plurality ofPDCCHs can be transmitted within a control region. The UE can monitorthe plurality of PDCCHs. The PDCCH is transmitted on an aggregation ofone or several consecutive control channel elements (CCEs). The CCE is alogical allocation unit used to provide the PDCCH with a coding ratebased on a state of a radio channel. The CCE corresponds to a pluralityof resource element groups (REGs). A format of the PDCCH and the numberof bits of the available PDCCH are determined by the number of CCEs. TheBS determines a PDCCH format according to DCI to be transmitted to theUE, and attaches a cyclic redundancy check (CRC) to control information.The CRC is masked with a unique identifier (referred to as a radionetwork temporary identifier (RNTI)) according to an owner or usage ofthe PDCCH. If the PDCCH is for a specific UE, a unique identifier (e.g.,cell-RNTI (C-RNTI)) of the UE may be masked to the CRC. Alternatively,if the PDCCH is for a paging message, a paging identifier (e.g.,paging-RNTI (P-RNTI)) may be masked to the CRC. If the PDCCH is forsystem information (more specifically, a system information block(SIB)), a system information RNTI (SI-RNTI) may be masked to the CRC.When the PDCCH is for a random access response, a random access-RNTI(RA-RNTI) may be masked to the CRC.

The PDCCH carries a message known as DCI which includes resourceassignment information and other control information for a UE or UEgroup. In general, a plurality of PDCCHs can be transmitted in asubframe. Each PDCCH is transmitted using one or more CCEs. Each CCEcorresponds to 9 sets of 4 REs. The 4 REs are referred to as an REG. 4QPSK symbols are mapped to one REG. REs allocated to a reference signalare not included in an REG, and thus the total number of REGs in OFDMsymbols depends on presence or absence of a cell-specific referencesignal. The concept of REG (i.e. group based mapping, each groupincluding 4 REs) is used for other downlink control channels (PCFICH andPHICH). That is, REG is used as a basic resource unit of a controlregion. 4 PDCCH formats are supported as shown in Table 2.

TABLE 2 Number of Number of PDCCH CCEs Number of PDCCH format (n) REGsbits 0 1 9 72 1 2 8 144 2 4 36 288 3 5 72 576

CCEs are sequentially numbered. To simplify a decoding process,transmission of a PDCCH having a format including n CCEs can be startedusing as many CCEs as a multiple of n. The number of CCEs used totransmit a specific PDCCH is determined by a BS according to channelcondition. For example, if a PDCCH is for a UE having a high-qualitydownlink channel (e.g. a channel close to the BS), only one CCE can beused for PDCCH transmission. However, for a UE having a poor channel(e.g. a channel close to a cell edge), 8 CCEs can be used for PDCCHtransmission in order to obtain sufficient robustness. In addition, apower level of the PDCCH can be controlled according to channelcondition.

LTE defines CCE positions in a limited set in which PDCCHs can bepositioned for each UE. CCE positions in a limited set that the UE needsto monitor in order to detect the PDCCH allocated thereto may bereferred to as a search space (SS). In LTE, the SS has a size dependingon PDCCH format. A UE-specific search space (USS) and a common searchspace (CSS) are separately defined. The USS is set per UE and the rangeof the CSS is signaled to all UEs. The USS and the CSS may overlap for agiven UE. In the case of a considerably small SS with respect to aspecific UE, when some CCEs positions are allocated in the SS, remainingCCEs are not present. Accordingly, the BS may not find CCE resources onwhich PDCCHs will be transmitted to available UEs within givensubframes. To minimize the possibility that this blocking continues tothe next subframe, a UE-specific hopping sequence is applied to thestarting point of the USS.

Table 3 shows sizes of the CSS and USS.

TABLE 3 Number of Number of Number of candidates candidates PDCCH CCEsin common in dedicated format (n) search space search space 0 1 — 6 1 2— 6 2 4 4 2 3 8 2 2

To control computational load of blind decoding based on the number ofblind decoding processes to an appropriate level, the UE is not requiredto simultaneously search for all defined DCI formats. In general, the UEsearches for formats 0 and 1A at all times in the USS. Formats 0 and 1Ahave the same size and are discriminated from each other by a flag in amessage. The UE may need to receive an additional format (e.g. format 1,1B or 2 according to PDSCH transmission mode set by a BS). The UEsearches for formats 1A and 1C in the CSS. Furthermore, the UE may beset to search for format 3 or 3A. Formats 3 and 3A have the same size asthat of formats 0 and 1A and may be discriminated from each other byscrambling CRC with different (common) identifiers rather than aUE-specific identifier. PDSCH transmission schemes and informationcontent of DCI formats according to transmission mode (TM) are arrangedbelow.

Transmission Mode (TM)

-   -   Transmission mode 1: Transmission from a single base station        antenna port    -   Transmission mode 2: Transmit diversity    -   Transmission mode 3: Open-loop spatial multiplexing    -   Transmission mode 4: Closed-loop spatial multiplexing    -   Transmission mode 5: Multi-user MIMO (Multiple Input Multiple        Output)    -   Transmission mode 6: Closed-loop rank-1 precoding    -   Transmission mode 7: Single-antenna port (ports) transmission    -   Transmission mode 8: Double layer transmission (ports 7 and 8)        or single-antenna port (port 7 or 8) transmission    -   Transmission mode 9: Transmission through up to 8 layers (ports        7 to 14) or single-antenna port (port 7 or 8) transmission

DCI Format

-   -   Format 0: Resource grants for PUSCH transmission    -   Format 1: Resource assignments for single codeword PDSCH        transmission (transmission modes 1, 2 and 7)    -   Format 1A: Compact signaling of resource assignments for single        codeword PDSCH (all modes)    -   Format 1B: Compact resource assignments for PDSCH using rank-1        closed loop precoding (mod 6)    -   Format 1C: Very compact resource assignments for PDSCH (e.g.        paging/broadcast system information)    -   Format 1D: Compact resource assignments for PDSCH using        multi-user MIMO (mode 5)    -   Format 2: Resource assignments for PDSCH for closed-loop MIMO        operation (mode 4)    -   Format 2A: Resource assignments for PDSCH for open-loop MIMO        operation (mode 3)    -   Format 3/3A: Power control commands for PUCCH and PUSCH with        2-bit/1-bit power adjustments

FIG. 5 illustrates an EPDCCH. The EPDCCH is a channel additionallyintroduced in LTE-A.

Referring to FIG. 5 , a PDCCH (for convenience, legacy PDCCH or L-PDCCH)according to legacy LTE may be allocated to a control region (see FIG. 4) of a subframe. In the figure, the L-PDCCH region means a region towhich a legacy PDCCH may be allocated. Meanwhile, a PDCCH may be furtherallocated to the data region (e.g., a resource region for a PDSCH). APDCCH allocated to the data region is referred to as an E-PDCCH. Asshown, control channel resources may be further acquired via the E-PDCCHto mitigate a scheduling restriction due to restricted control channelresources of the L-PDCCH region. Similarly to the L-PDCCH, the E-PDCCHcarries DCI. For example, the E-PDCCH may carry downlink schedulinginformation and uplink scheduling information. For example, the UE mayreceive the E-PDCCH and receive data/control information via a PDSCHcorresponding to the E-PDCCH. In addition, the UE may receive theE-PDCCH and transmit data/control information via a PUSCH correspondingto the E-PDCCH. The E-PDCCH/PDSCH may be allocated starting from a firstOFDM symbol of the subframe, according to cell type. In thisspecification, the PDCCH includes both L-PDCCH and EPDCCH unlessotherwise noted.

FIG. 6 illustrates a structure of an uplink subframe used in LTE(-A).

Referring to FIG. 6 , a subframe 500 is composed of two 0.5 ms slots501. Assuming a length of a normal cyclic prefix (CP), each slot iscomposed of 7 symbols 502 and one symbol corresponds to one SC-FDMAsymbol. A resource block (RB) 503 is a resource allocation unitcorresponding to 12 subcarriers in the frequency domain and one slot inthe time domain. The structure of the uplink subframe of LTE(-A) islargely divided into a data region 504 and a control region 505. A dataregion refers to a communication resource used for transmission of datasuch as voice, a packet, etc. transmitted to each UE and includes aphysical uplink shared channel (PUSCH). A control region refers to acommunication resource for transmission of an uplink control signal, forexample, downlink channel quality report from each UE, receptionACK/NACK for a downlink signal, uplink scheduling request, etc. andincludes a physical uplink control channel (PUCCH). A sounding referencesignal (SRS) is transmitted through an SC-FDMA symbol that is lastlypositioned in the time axis in one subframe. SRSs of a plurality of UEs,which are transmitted to the last SC-FDMAs of the same subframe, can bedifferentiated according to frequency positions/sequences. The SRS isused to transmit an uplink channel state to an eNB and is periodicallytransmitted according to a subframe period/offset set by a higher layer(e.g., RRC layer) or aperiodically transmitted at the request of theeNB.

Next, HARQ (Hybrid Automatic Repeat reQuest) will be described. Whenthere are a plurality of UEs having data to be transmitted onuplink/downlink in a wireless communication, an eNB selects UEs whichwill transmit data per transmission time internal (TTI) (e.g.,subframe). In a system using multiple carriers and the like, an eNBselects UEs which will transmit data on uplink/downlink per TTI and alsoselects a frequency band to be used for data transmission of thecorresponding UEs.

When description is based on uplink (UL), UEs transmit reference signals(or pilot signals) on uplink and an eNB detects channel states of theUEs using the reference signals transmitted from the UEs and selects UEswhich will transmit data on uplink in each unit frequency band per TTI.The eNB notifies the UEs of the result of selection. That is, the eNBtransmits, to UL scheduled UEs, a UL assignment message indicating thatthe UEs may transmit data using a specific frequency band in a specificTTI. The UL assignment message is also referred to as a UL grant. TheUEs transmit data on uplink according to the UL assignment message. TheUL assignment message may include UE identity (ID), RB allocationinformation, a modulation and coding scheme (MCS), a redundancy version(RV), new data indication (NDI) and the like.

In the case of synchronous HARQ, a retransmission time is appointed inthe system (e.g., after 4 subframes from a NACK reception time)(synchronous HARQ). Accordingly, the eNB may send a UL grant message toUEs only in initial transmission and subsequent retransmission isperformed according to an ACK/NACK signal (e.g., PHICH signal). In thecase of asynchronous HARQ, a retransmission time is not appointed andthus the eNB needs to send a retransmission request message to UEs.Further, frequency resources or an MCS for retransmission are identicalto those in previous transmission in the case of non-adaptive HARQ,whereas frequency resources or an MCS for retransmission may differ fromthose in previous transmission in the case of adaptive HARQ. Forexample, in the case of asynchronous adaptive HARQ, the retransmissionrequest message may include UE ID, RB allocation information, HARQprocess ID/number, RV and NDI information because frequency resources oran MCS for retransmission vary with transmission time.

FIG. 7 illustrates a UL HARQ operation in an LTE(-A) system. In theLTE(-A) system, asynchronous adaptive HARQ is used as UL HARQ. When8-channel HARQ is used, 0 to 7 are provided as HARQ process numbers. OneHARQ process operates per TTI (e.g., subframe). Referring to FIG. 7 , aUL grant is transmitted to a UE 120 through a PDCCH (S600). The UE 120transmits UL data to an eNB 110 after 4 subframes from the time (e.g.,subframe 0) at which the UL grant is received using an RB and an MCSdesignated by the UL grant (S602). The eNB 110 decodes the UL datareceived from the UE 120 and then generates ACK/NACK. When decoding ofthe UL data fails, the eNB 110 transmits NACK to the UE 120 (S604). TheUE 120 retransmits the UL data after 4 subframes from the time at whichNACK is received (S606). Initial transmission and retransmission of theUL data are performed through the same HARQ process (e.g., HARQ process4). ACK/NACK information may be transmitted through a PHICH.

A description will be given of TDD signal transmission timing in asingle carrier (or cell) situation with reference to FIGS. 8 to 14 .

FIGS. 8 and 9 illustrate PDSCH-UL ACK/NACK timing. Here, UL ACK/NACKrefers to ACK/NACK transmitted on uplink in response to DL data (e.g.,PDSCH).

Referring to FIG. 8 , a UE can receive one or more PDSCH signals in M DLsubframes (SFs) (S502_0 to S502_M−1). Each PDSCH signal is used totransmit one or more (e.g. 2) transport blocks (TBs) according totransmission mode. A PDCCH signal indicating SPS (Semi-PersistentScheduling) may also be received in step S502_0 to S502_M−1, which isnot shown. When a PDSCH signal and/or an SPS release PDCCH signal ispresent in the M DL subframes, the UE transmits ACK/NACK through a ULsubframe corresponding to the M DL subframes via processes fortransmitting ACK/NACK (e.g. ACK/NACK (payload) generation, ACK/NACKresource allocation, etc.) (S504). ACK/NACK includes acknowledgementinformation about the PDSCH signal and/or an SPS release PDCCH receivedin step S502_0 to S502_M−1. While ACK/NACK is transmitted through aPUCCH basically, ACK/NACK is transmitted through a PUSCH when a PUSCH istransmitted at ACK/NACK transmission time. Various PUCCH formats shownin Table 3 can be used for ACK/NACK transmission. To reduce the numberof ACK/NACK bits transmitted through a PUCCH format, various methodssuch as ACK/NACK bundling and ACK/NACK channel selection can be used.

As described above, in TDD, ACK/NACK relating to data received in the MDL subframes is transmitted through one UL subframe (i.e. M DL SF(s): 1UL SF) and the relationship therebetween is determined by a DASI(Downlink Association Set Index).

Table 4 shows DASI (K: {k0, k1, . . . , k−1}) defined in LTE(-A). Table4 shows spacing between a UL subframe transmitting ACK/NACK and a DLsubframe relating to the UL subframe. Specifically, when a PDCCH thatindicates PDSCH transmission and/or SPS release is present in a subframen−k (k∈K), the UE transmits ACK/NACK in a subframe n.

TABLE 4 TDD UL-DL Subframe n Configuration 0 1 2 3 4 5 6 7 8 9 0 — — 6 —4 — — 6 — 4 1 — — 7, 6 4 — — — 7, 6 4 — 2 — — 8, 7, 4, 6 — — — — 8, 7,4, 6 — — 3 — — 7, 6, 11 6, 5 5,4 — — — — — 4 — — 12, 8,7, 11 6, 5, 4, 7— — — — — — 5 — — 13, 12, 9, 8, 7, — — — — — — — 5, 4, 11, 6 6 — — 7 7 5— — 7 7 —

FIG. 9 illustrates UL ACK/NACK transmission timing when UL-DLconfiguration #1 is configured. In the figure, SF #0 to #9 and SF #10 to#19 respectively correspond to radio frames, and numerals in blocksdenote UL subframes relating to DL subframes. For example, ACK/NACK fora PDSCH of SF #5 is transmitted in SF #5+7 (=SF #12) and ACK/NACK for aPDSCH of SF #6 is transmitted in SF #6+6 (=SF #12). Accordingly, bothACKs/NACKs for DL signals of SF #5/#6 are transmitted in SF #12.Similarly, ACK/NACK for a PDSCH of SF #14 is transmitted in SF #14+4(=SF #18).

FIGS. 10 and 11 illustrate PHICH grant-PUSCH timing. A PUSCH can betransmitted corresponding to a PDCCH (UL grant) and/or a PHICH (NACK).

Referring to FIG. 10 , the UE can receive a PDCCH (UL grant) and/or aPHICH (NACK) through a PDCCH (S702). Here, NACK corresponds to anACK/NACK response to previous PUSCH transmission. In this case, the UEcan initially transmit/retransmit one or more TBs through a PUSCH afterk subframes via processes for PUSCH transmission (e.g. TB coding, TB-CWswiping, PUSCH resource allocation, etc.) (S704). The present embodimentis based on the assumption that a normal HARQ operation in which a PUSCHis transmitted once is performed. In this case, a PHICH and a UL grantcorresponding to PUSCH transmission are present in the same subframe.However, in case of subframe bundling in which a PUSCH is transmittedmultiple times through a plurality of subframes, a PHICH and a UL grantcorresponding to PUSCH transmission may be present in differentsubframes.

Table 5 shows a UAI (Unlink Association Index) (k) for PUSCHtransmission in LTE(-A). Table 5 shows spacing between a DL subframefrom which a PHICH/UL grant is detected and a UL subframe relating tothe DL subframe. Specifically, when a PHICH/UL grant is detected from asubframe n, the UE can transmit a PUSCH in a subframe n+k.

TABLE 5 TDD UL-DL subframe number n Configuration 0 1 2 3 4 5 6 7 8 9 04 6 4 6 1 6 4 6 4 2 4 4 3 4 4 4 4 4 4 5 4 6 7 7 7 7 5

FIG. 11 illustrates PUSCH transmission timing when UL-DL configuration#1 is configured. In the figure, SF #0 to #9 and SF #10 to #19respectively correspond to radio frames, and numerals in blocks denoteUL subframes relating to DL subframes. For example, a PUSCHcorresponding to PHICH/UL grant of SF #6 is transmitted in SF #6+6 (=SF#12) and a PUSCH corresponding to a PHICH/UL grant of SF #14 istransmitted in SF #14+4 (=SF #18).

FIGS. 12 and 13 illustrate PUSCH-PHICH/UL grant timing. A PHICH is usedto transmit DL ACK/NACK. Here, DL ACK/NACK means ACK/NACK transmitted ondownlink as a response to UL data (e.g. PUSCH).

Referring to FIG. 12 , the UE transmits a PUSCH signal to the BS (S902).Here, the PUSCH signal is used to transmit one or a plurality of (e.g.2) TBs according to transmission mode. The BS can transmit ACK/NACK as aresponse to PUSCH transmission through a PHICH after k subframes viaprocesses for ACK/NACK transmission (e.g. ACK/NACK generation, ACK/NACKresource allocation, etc.) (S904). ACK/NACK includes acknowledgementinformation about the PUSCH signal of step S902. When a response toPUSCH transmission is NACK, the BS can transmit a UL grant PDCCH forPUSCH retransmission to the UE after k subframe (S904). The presentembodiment is based on the assumption that a normal HARQ operation inwhich a PUSCH is transmitted once is performed. In this case, a PHICHand UL grant used for PUSCH transmission can be transmitted in the samesubframe. In case of subframe bundling, however, the PHICH and UL grantused for PUSCH transmission can be transmitted in different subframes.

Table 6 shows a UAI for PHICH/UL grant transmission in LTE(-A). Table 6shows spacing between a DL subframe in which a PHICH/UL grant is presentand a UL subframe relating to the DL subframe. Specifically, a PHICH/ULgrant of a subframe i corresponds to PUSCH transmission through asubframe i−k.

TABLE 6 TDD UL-DL subframe number i Configuration 0 1 2 3 4 5 6 7 8 9 07 4 7 4 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 6 4 7 4 6

FIG. 13 illustrates PHICH/UL grant transmission timing when UL-DLconfiguration #1 is configured. In the figure, SF #0 to #9 and SF #10 to#19 respectively correspond to radio frames, and numerals in blocksdenote DL subframes relating to UL subframes. For example, a PHICH/ULgrant corresponding to a PUSCH of SF #2 is transmitted in SF #2+4 (=SF#6) and a PHICH/UL grant corresponding to a PUSCH of SF #8 istransmitted in SF #8+6 (=SF #14).

PHICH resource allocation will now be described. When a PUSCH istransmitted in subframe #n, the UE determines a PHICH resourcecorresponding to the PUSCH in subframe #(n+k_(PHICH)). In case of FDD,k_(PHICH) has a fixed value (e.g. 4). In case of TDD, k_(PHICH) has avalue depending on UL-DL configuration. Table 7 shows k_(PHICH) for TDDis equivalent to Table 6.

TABLE 7 TDD UL-DL UL subframe index n Configuration 0 1 2 3 4 5 6 7 8 90 4 7 6 4 7 6 1 4 6 4 6 2 6 6 3 6 6 6 4 6 6 5 6 6 4 6 6 4 7

A PHICH resource is provided by [PHICH group index, orthogonal sequenceindex]. The PHICH group index and the orthogonal sequence index aredetermined using (i) a lowest PRB index used for PUSCH transmission and(ii) a 3-bit field value for DMRS (Demodulation Reference Signal) cyclicshift. Here, (i) and (ii) are indicated by a UL grant PDCCH.

A description will be given of a HARQ process. The UE executes aplurality of parallel HARQ processes for UL transmission. The pluralityof parallel HARQ processes is used to continuously perform ULtransmission while the UE waits for HARQ feedback representing whetherprevious UL transmission has been successful or not. Each HARQ processrelates to a HARQ buffer of a MAC (Medium Access Control) layer. EachHARQ process manages the number of transmissions of a MAC PDU (PhysicalData Unit) in the buffer, HARQ feedback for the MAC PDU in the buffer,and a state parameter regarding a current redundancy version.

In case of LTE(-A) FDD, the number of UL HARQ processes for non-subframebundling operation (i.e. normal HARQ operation) is 8. In case of LTE(-A)TDD, the number of UL HARQ processes and HARQ RTT (Round Trip Time) areconfigured differently according to DL-UL configurations because thenumber of UL subframes depends on UL-DL configuration. Here, the HARQRTT may be a time interval (in the unit of SF or ms, for example)between a time when a UL grant is received and a time when a PHICH(corresponding to the UL grant) is received through transmission of aPUSCH (corresponding the UL grant) or a time interval between a PUSCHtransmission time and a PUSCH retransmission time.

The number of UL HARQ processes varies. When subframe bundling isapplied, a bundle of PUSCHs configured of 4 contiguous UL subframes istransmitted in FDD and TDD. Accordingly, a HARQ operation/process whensubframe bundling is applied is different from the normal HARQoperation/process.

Table 8 shows the number of synchronous UL HARQ processes and HARQ RTTin TDD. When the UL HARQ RTT is 10 [SFs or ms] (UL-DL configurations #1,#2, #3, #4 and #5), one UL HARQ process uses one fixed UL SF timing.When the UL HARQ RTT does not correspond to 10 [SFs or ms] (UL-DLconfigurations #0 and #6), one UL HARQ process uses a plurality of UL SFtimings (instead of one fixed UL SF timing) while hopping. For example,in case of UL-DL configuration #6, PUSCH transmission timings in one ULHARQ process are: SF #2: PUSCH=>SF #13: PUSCH (RTT: 11 SFs)=>SF #24:PUSCH (RTT: 11 SFs)=>SF #37: PUSCH (RTT: 13 SFs)=>SF #48: PUSCH (RTT: 11SFs)=>SF #52: PUSCH (RTT: 14 SFs).

TABLE 8 Number of HARQ processes UL-DL Number of for normalconfiguration UL SFs HARQ operation HARQ RTT 0 6 7 11 or 13 1 4 4 10 2 22 10 3 3 3 10 4 2 2 10 5 1 1 10 6 5 6 11 or 13 or 14

In case of TDD UL-DL configurations #1 to #6 and normal HARQ operation,the UE transmits a corresponding PUSCH signal in subframe n+k (refer toTable 5) according to UL grant PDCCH and/or PHICH information upondetection of the UL grant PDCCH and/or PHICH information in subframe n.

In case of TDD UL-DL configuration #0 and the normal HARQ operation,when a UL DCI grant PDCCH and/or a PHICH are detected from subframe n,PUSCH transmission timing of the UE is varied according to conditions.When the MSB (Most Significant bit) of a UL index in DCI is 1 or thePHICH is received through a resource corresponding to I_(PHICH)=0 insubframe #0 or #5, the UE transmits the corresponding PUSCH signal insubframe n+k (refer to Table 5). When the LSB (Least Significant bit) ofthe UL index in the DCI is 1, the PHICH is received through a resourcecorresponding to I_(PHICH)=1 in subframe #0 or #5, or the PHICH isreceived in subframe #1 or #6, UE transmits the corresponding PUSCHsignal in subframe n+7. When both the MSB and LSB in the DCI are set,the UE transmits the corresponding PUSCH signal in subframe n+k (referto Table 5) and subframe n+7.

FIG. 14 illustrates a synchronous UL HARQ process when UL-DLconfiguration #1 is configured. Numerals in blocks denote UL HARQprocess numbers. The synchronous UL HARQ process shown in FIG. 14corresponds to a normal HARQ process. Referring to FIG. 14 , HARQprocess #1 involves SF #2, SF #6, SF #12 and SF #16. For example, if aninitial PUSCH signal (e.g. RV=0) is transmitted in SF #2, a UL grantPDCCH and/or a PHICH corresponding to the PUSCH signal can be receivedin SF #6 and a (retransmission) PUSCH signal (e.g. RV=2) correspondingto the initial PUSCH signal can be transmitted in SF #12. Accordingly, 4UL HARQ processes having an RTT (Round Trip Time) of 10 SFs (or 10 ms)are present in case of UL-DL configuration #1.

FIG. 15 illustrates carrier aggregation (CA) communication system.

Referring to FIG. 15 , a plurality of UL/DL component carriers (CCs) canbe aggregated to support a wider UL/DL bandwidth. The CCs may becontiguous or non-contiguous in the frequency domain. Bandwidths of theCCs can be independently determined. Asymmetrical CA in which the numberof UL CCs is different from the number of DL CCs can be implemented.Control information may be transmitted/received only through a specificCC. This specific CC may be referred to as a primary CC and other CCsmay be referred to as secondary CCs. For example, when cross-carrierscheduling (or cross-CC scheduling) is applied, a PDCCH for downlinkallocation can be transmitted on DL CC #0 and a PDSCH correspondingthereto can be transmitted on DL CC #2. The term “component carrier” maybe replaced by other equivalent terms (e.g. “carrier”, “cell”, etc.).

For cross-CC scheduling, a carrier indicator field (CIF) is used.Presence or absence of the CIF in a PDCCH can be determined by higherlayer signaling (e.g. RRC signaling) semi-statically and UE-specifically(or UE group-specifically). The baseline of PDCCH transmission issummarized as follows.

-   -   CIF disabled: a PDCCH on a DL CC is used to allocate a PDSCH        resource on the same DL CC or a PUSCH resource on a linked UL        CC.    -   No CIF    -   CIF enabled: a PDCCH on a DL CC can be used to allocate a PDSCH        or PUSCH resource on a specific DL/UL CC from among a plurality        of aggregated DL/UL CCs using the CIF.    -   LTE DCI format extended to have CIF    -   CIF corresponds to a fixed x-bit field (e.g. x=3) (when CIF is        set)    -   CIF position is fixed irrespective of DIC format size (when CIF        is set)

When the CIF is present, the BS may allocate a monitoring DL CC (set) toreduce BD complexity of the UE. For PDSCH/PUSCH scheduling, the UE maydetect/decode a PDCCH only on the corresponding DL CCs. The BS maytransmit the PDCCH only through the monitoring DL CC (set). Themonitoring DL CC set may be set UE-specifically, UE-group-specificallyor cell-specifically.

FIG. 16 illustrates scheduling when a plurality of carriers isaggregated. It is assumed that 3 DL CCs are aggregated and DL CC A isset to a PDCCH CC. DL CC A-C may be referred to as a serving CC, servingcarrier, serving cell, etc. When the CIF is disabled, each DL CC cantransmit only a PDCCH that schedules a PDSCH corresponding to the DL CCwithout a CIF according to LTE PDCCH rule (non-cross-CC scheduling).When the CIF is enabled through UE-specific (or UE-group-specific orcell-specific) higher layer signaling, a specific CC (e.g. DL CC A) cantransmit not only the PDCCH that schedules the PDSCH of DL CC A but alsoPDCCHs that schedule PDSCHs of other DL CCs using the CIF(cross-scheduling). A PDCCH is not transmitted on DL CC B and DL CC C.

Meanwhile, a next generation RAT (radio access technology) isconsidering a self-contained subframe to minimize data transmissionlatency. FIG. 17 illustrates a structure of a self-contained subframe.In FIG. 17 , oblique line areas indicate DL control regions and blackcolored areas indicate UL control regions. Areas having no mark may beused for DL data transmission or UL data transmission. In thisstructure, DL transmission and UL transmission are performed in dueorder within one subframe, whereby DL data transmission and UL ACK/NACKtransmission can be performed within the subframe. Or, UL granttransmission and UL data reception can be performed within the subframeas well. As a result, the time required for data re-transmission may bereduced when an error occurs in data transmission, whereby latency offinal data transfer may be minimized.

Examples of the self-contained subframe type that may be configured inthe system may consider four subframe types as follows. The periods arearranged in temporal order.

-   -   DL control period+DL data period+GP (guard period)+UL control        period    -   DL control period+DL data period    -   DL control period+GP+UL data period+UL control period    -   DL control period+GP+UL data period

PDFICH, PHICH, and PDCCH can be transmitted in a DL control period andPDSCH can be transmitted in a DL data period. PUCCH can be transmittedin a UL control period and PUSCH can be transmitted in a UL data period.A time gap for switching from a transmission mode to a reception mode orvice versa is required for an eNB and a UE. A GP provides the time gap.To this end, some OFDM symbols at the time when DL is switched to UL inthe self-contained subframe structure are configured as a GP.

Embodiment

A new radio access technology (RAT) system may be designed to supportvarious use scenarios (or service types and traffic types) such asenhanced mobile broadband (eMBB), ultra-reliable and low latencycommunications (URLLC), massive machine type communications (mMTC), andso on. The various use scenarios (hereinafter, referred to as use cases)may have different requirements, particularly in terms of (user-plane)latency. For example, the respective use cases may require different(maximum) latencies in the order of URLLC (e.g., 0.5 ms)<eMBB (e.g., 4ms)<mMTC (e.g., Xms>4 ms). Accordingly, a different TTI length may beset for each use case. For example, different TTI lengths may be givenin the order of URLLC<eMBB<mMTC. Herein, a TTI may be defined as a(minimum) time interval between data schedulings or a (maximum)transmission time duration of single data. The (minimum) time intervalbetween data schedulings or the (maximum) transmission time duration ofsingle data may be represented as an integer/real number multiple of asubframe (SF) or slot, or as an integer multiple of OFDM symbols.

Meanwhile, configuration of an HARQ timing and operation of an HARQprocess for DL/UL data scheduling/transmission may vary according to alatency requirement/TTI length (a use case represented by the latencyrequirement/TTI length), and a UE capability related to DL/UL signalprocessing (e.g., DL control/data channel decoding, UL transmissionpreparation including encoding, etc.). For example, a (minimum) HARQtiming latency may be set to be smaller for URLLC than for eMBB, whereasthe (maximum) number of HARQ processes may be set to be larger for eMBBthan for URLLC. Herein, an HARQ timing may represent a delay between DLdata reception and HARQ-ACK transmission, a delay between UL grantreception and UL data transmission, or the like, expressed as an integermultiple of a TTI.

Hereinafter, effective methods for configuring DL/UL HARQ timings andoperating the HARQ processes considering use cases (or different TTIlengths corresponding thereto) requiring different latencies areproposed. As used herein, (i) TTI and SF may have the same meaning interms of time length or time period (e.g., an SF offset may beconsidered as a TTI offset), or (ii) TTI length may be set to differentvalues for respective use cases, and the SF length may be set to asingle value that is common to all use cases (e.g., the SF may have thesame time duration as a particular one of multiple possible TTIlengths). In the case of (ii), (ii-1) SF may be set to have the sametime duration as the minimum TTI (e.g., the TTI length set in URLLC), or(ii-2) SF may be set to have the same time duration as a normal TTI(e.g., a TTI length set in eMBB). In the case of (ii-1), one TTIconfigured in a specific use case may be composed of one or multiple SFs(or slots). In the case of (ii-2), one TTI configured in a specific usecase may be composed of one or multiple SFs (or slots), or a pluralityof TTIs may be configured in one SF (or slot).

For convenience of description, the (minimum) HARQ timing latenciesrequired by the UE and the BS are defined as follows.

1) dUE_DL: a delay between DL data reception and HARQ-ACK transmission(at the UE). The UE may report dUE_DL information (capability) thereofto the BS at an appropriate time (e.g., in the initial access or RRCconnection procedure). The dUE_DL information and dUE_UL informationdescribed below may be supported differently for the same UE.

2) dNB_DL: a delay between HARQ-ACK reception and DL data retransmission(at the BS). The BS may signal the dNB_DL information to the UE at anappropriate time. The dNB_DL information may be configured differentlyfrom dNB_UL information described below. Alternatively, the BS maysignal the following RTT_DL or HARQ_DL information to the UE at anappropriate time, and the UE may calculate the dNB_DL information basedon the RTT_DL or HARQ_DL information.

3) RTT_DL: a (minimum) delay between DL data transmissions of the sameHARQ process (e.g., dUE_DL+dNB_DL)

4) Harq_DL: a (maximum) number of DL HARQ processes (e.g. the maximumnumber of TTIs within RTT_DL). The number of bits for designating theHARQ process ID in the DL grant DCI and/or the number of the initialbits to be stored per DL data (e.g., TB) or HARQ process from theperspective of the DL soft buffer may be determined differentlyaccording to the value of HARQ_DL.

5) dUE_UL: a delay between UL grant reception and UL data transmission(at the UE). The UE may report dUE_UL information (capability) thereofto the BS at an appropriate time (e.g., in the initial access or RRCconnection procedure). The dUE_UL information and dUE_DL information maybe supported differently for the same UE.

6) dNB_UL: a delay between UL data reception and transmission ofretransmitted UL grant (at the BS). The BS may signal the dNB_ULinformation to the UE at an appropriate time. The dNB_UL information maybe configured differently from the dNB_DL information. Alternatively,the BS may signal the following RTT_UL or Harq_UL information to the UEat an appropriate time, and the UE may calculate the dNB_UL informationbased on the RTT_UL or Harq_UL information.

7) RTT_UL: a (minimum) delay between UL data transmissions of the sameHARQ process (e.g. dUE_UL+dNB_UL)

8) Harq_UL: a (maximum) UL HARQ process number (e.g. the maximum numberof TTIs within RTT_UL). The number of bits for designating the HARQprocess ID in the UL grant DCI and/or the number of the initial bits tobe buffered per UL data (e.g., TB) or HARQ process from the perspectiveof the UL soft buffer may be determined differently according to thevalue of Harq_UL.

FIGS. 18 to 21 illustrate transmission and reception of signalsaccording to a HARQ timing latency. Referring to the figures, the UE maytransmit HARQ-ACK dUE_DL after receiving DL data. If the HARQ-ACK isNACK, the BS may retransmit the DL data after dNB_DL. Similarly, the UEmay transmit UL data (e.g., PUSCH) dUE_UL after receiving UL grant. Ifretransmission of the UL data needs to be performed, the BS may transmita UL grant indicating retransmission of UL data after dNB_UL.

As used herein, the terms TTI length, use case, and subcarrier (SC)spacing (SCS) used in the OFDM modulation and demodulation may havesimilar meanings or be replaced with each other. For example, a shortTTI length may have a similar meaning to a large SCS or URLLC, and along TTI length may have a similar meaning to a small SCS or mMTC. Thenormal TTI length (between the short TTI length and the long TTI length)may have a similar meaning to the normal SCS or eMBB (between the smallSCS and the large SCS). The HARQ timing latency may be given as aninteger multiple (or a real number multiple) of an SF/slot/TTI length orgiven as an integer multiple of an OFDM symbol interval. Here, the OFDMsymbol refers to OFDM-based symbols (e.g., an OFDM symbol, an SC-FDMAsymbol, etc.), and may be expressed simply as a symbol. The TTI lengthmay be used in a similar meaning to or replaced with the number of SFs/slots/symbols constituting a single TTI, i.e., the number of SFs/slots/symbols per TTI. For example, the long TTI length may have asimilar meaning to a case where the number of SF/slots/symbols per TTIis large, and the short TTI length may have a similar meaning to a casewhere the number of SF/slots/symbols per TTI is small. As used herein,the terms TTI, SF and slot may be interchangeably used. In addition, inthis specification, the terms “long/short/increase/decrease” may mean“relatively long/short/increase/decrease” or mean“long/short/increase/decrease” with respect to a specific referencevalue. In the latter case, when it is assumed, for example, that theHARQ timing latency (or the minimum HARQ RTT) for TTI length X is set toA TTIs and the HARQ timing latency (or the minimum HARQ RTT) for TTIlength Y is set to B TTIs, it may be described that the HARQ timinglatency (or the minimum HARQ RTT) of one of the two TTI lengths X and Yis longer/shorter/increased/decreased, depending on the magnituderelationship between A and B. In this specification, eNB and gNB may beused interchangeably. In addition, the schemes described below may becombined with each other.

[Scheme 1] HARQ Processing Delay and HARQ Process Number

In this scheme, a method for managing a data processing delay, thenumber of HARQ processes associated therewith, and a reception buffer ina terminal (e.g., a UE) and a BS (e.g., an eNB) are proposed.Hereinafter, a HARQ (processing) delay may refer to (i) a time delaydUE_DL between a DL data reception time and a corresponding HARQ-ACKtransmission time, or (ii) a time delay dUE_UL between a UL grantreception time and a corresponding UL data transmission time. Inaddition, for the eNB, the HARQ (processing) delay may refer to (i) atime delay dNB_DL between a HARQ-ACK reception time and a correspondingretransmission DL data scheduling (DL grant transmission) time, or (ii)a time delay (dNB_UL) between a UL data transmission time and acorresponding retransmission UL data scheduling (UL grant transmission)time. The (minimum) HARQ RTT may refer to the (minimum) time delayRTT_DL, RTT_UL between a DL (or UL) data transmission (scheduling) timeand a corresponding DL (or UL) data retransmission (scheduling) time(having the same HARQ process ID as the corresponding data).

(1) HARQ Processing Delay

A. UE Delay

i. Capable min UE delay (min_dUE_cap): Minimum HARQ delay supportable bya UE according to the category and capability/implementation of the UE

ii. Configured min UE delay (min_due_cfg): Minimum HARQ delay among thecandidate HARQ delays that the eNB has configured for the UE

iii. Configured max UE delay (max_due_cfg): Maximum HARQ delay among thecandidate HARQ delays that the eNB has configured for the UE. Themaximum configurable value of max_due_cfg may be set to the same valueas dUE_default given below.

iv. Default UE delay (dUE_default): A HARQ delay of a UE that the UEassumes/applies before a HARQ delay is set for the UE by the eNB or inthe random access procedure

B. eNB Delay

i. Capable min eNB delay (min_dNB_cap): Minimum HARQ delay supportableby the eNB according to implementation of the eNB and cell management

ii. Configured min eNB delay (min_dNB_cfg): Minimum HARQ delay that isset for the UE by the eNB and may be taken at the eNB

1. In a period of min_dNB_cfg form the time of HARQ-ACK transmission fora specific DL HARQ process ID, the UE may operate, assuming/consideringthat there is no scheduling of DL data (retransmission) having the DLHARQ process ID (corresponding DL grant reception). For example, even ifthe UE receives scheduling information (e.g., DL grant) about the data(retransmission) having the DL HARQ process ID, the UE may skip thedecoding operation for the DL data (retransmission).

2. In a period of min_dNB_cfg from the time of UL data transmissionhaving a specific UL HARQ process ID, the UE may operate,assuming/considering that there is no scheduling of UL data(retransmission) having the UL HARQ process ID (corresponding UL grantreception). For example, even if the UE receives scheduling information(e.g., UL grant) about the data (retransmission) having the UL HARQprocess ID, the UE may skip the transmission operation for the UL data(retransmission).

3. min_dNB_cfg may be set to one value regardless of (resetting of) themin UE delay value. As another example, min_dNB_cfg may be automaticallyset (to, for example, a value equal to the min UE delay or a valueproportional to the min UE delay) according to the min UE delay valuewithout separate setting. As another example, min_dNB_cfg may beautomatically set according to the max HARQ num value set by the eNB(to, for example, a value obtained by subtracting min UE delay from maxHARQ num).

4. The maximum possible value of min_dNB_cfg may be set to the samevalue as the dNB_default given below.

iii. Default eNB delay (dNB_default): a HARQ delay of the eNB that theUE assumes/applies before a HARQ delay is set for the UE by the eNB orin the random access procedure. It may be predefined in a technicaldocument or may be set by the eNB (through, for example, specificbroadcast signaling or system information).

In the following description, min UE delay may refer to min_dUE_cap ormin_dUE_cfg, UE max delay may refer to max_dUE_cfg, and min eNB delaymay refer to min_dNB_cap or min_dNB_cfg.

(2) HARQ RTT and Process Number

A. HARQ RTT

i. Min HARQ RTT (min_RTT): Minimum HARQ retransmission delay supportableby a combination of min UE delay and min eNB delay or a combination ofmax UE delay and min eNB delay

1. In a period of min_RTT from the time of DL data scheduling having aspecific DL HARQ process ID (corresponding DL grant reception), the UEmay operate, assuming/considering that there is no scheduling of DL data(retransmission) having the HARQ process ID (DL grant reception). Forexample, even if the UE receives scheduling information (e.g., DL grant)about the data (retransmission) having the HARQ process ID, the UE mayskip the decoding operation for the DL data (retransmission).

2. In a period of min_RTT from the time of UL data scheduling having aspecific UL HARQ process ID (corresponding UL grant reception), the UEmay operate, assuming/considering that there is no scheduling of UL data(retransmission) having the HARQ process ID (UL grant reception). Forexample, even if the UE receives scheduling information (e.g., UL grant)about the data (retransmission) having the UL HARQ process ID, the UEmay skip the transmission operation for the UL data (retransmission).

3. min_RTT may be determined to be the sum of the min_due_cfg value (orthe max_due_cfg value) and the min_dNB_cfg value, or may be set by theeNB.

4. The maximum possible value of min HARQ RTT may be set to the samevalue as RTT_default given below.

Ii. Default HARQ RTT (RTT_default): Minimum HARQ retransmission delaysupportable by the combination of the default UE delay and the defaulteNB delay

1. RTT_default may be determined to be the sum of dUE_default anddNB_default.

2. RTT_default may be predefined in a technical document or may be setby the eNB (through, for example, specific broadcast signaling or systeminformation).

B. HARQ Process Number

i. Actual max HARQ num (max_N_act): Maximum number of HARQ processesthat may be divided (into individual TBs) either through a field of thescheduling DCI or from the perspective of processing of the MAC layer

1. Max_N_act may be automatically set according to the combination ofthe min UE delay (or max delay UE) and the min eNB delay (e.g., it maybe automatically set to a value corresponding to min_RTT or the numberof SFs (or TTIs) within the period of min HARQ RTT), or may be set bythe eNB.

2. The maximum possible value (and minimum possible value) of max_N_actmay be limited, and the maximum value (and minimum value) may be setdifferently (proportionally) according to the values of min UE delay (ormax UE delay), min eNB delay, and min HARQ RTT.

3. The maximum possible value of max_N_act may be set to the same valueas default max HARQ num given below.

ii. Reference max HARQ num (max_N_ref): Maximum number of HARQ processesthat is used as a basis for partitioning/allocating a reception softbuffer (e.g., determining the minimum number of stored bits per TB)

1. Max_N_ref may be predefined to have a specific value (in a technicaldocument), set to a value corresponding to min_RTT (or the number of SFs(or TTIs) within the period of min HARQ RTT), or configured by the eNB.

2. As an example, actual soft buffer partitioning (e.g., determining theminimum number of stored bits per TB) may be performed based on min(max_N_ref, max_N_act) or max_N_ref.

iii. Default max HARQ num (N_default): Maximum number of HARQ processesthat the UE assumes/applies at the point in time before HARQ delay, minHARQ RTT, or max HARQ num is set for the UE by the eNB or in the randomaccess procedure.

1. N_default may be set to the same value as max_N_ref, or may beautomatically set by a combination of dUE_default and dNB_default (e.g.,it may be set to a value corresponding to RTT_default or to the numberof SFs (or TTIs) within the period of default HARQ RTT). Alternatively,N_default may be set to the number of HARQ processes corresponding tothe maximum HARQ RTT (Ymax i ms: maximum time in which peak rate datacan be successively received/stored).

2. N_default may be predefined in a technical document or may be set bythe eNB (through, for example, specific broadcast signaling or systeminformation).

In the following description, max HARQ num may refer to actual max HARQnum. Min HARQ RTT used in determining max HA RQ num may have thefollowing meanings according to the DL/UL configuration attribute.

-   -   For dynamic TDD (DL/UL configuration is changed dynamically), it        may refer to the number of SFs (or TTIs) in RTT regardless of        DL/UL.    -   For semi-static DL/UL configuration-based TDD or FDD, it may        refer to the number of DL SFs (or TTIs) in RTT in the case of DL        and refer to the number of UL SFs (or TTIs) in RTT in the case        of UL.

(3) HARQ Parameter Setting #1

A. Method 1-1: Determination Only by Min UE Delay (or Max UE Delay)

With only min UE delay (and max UE delay) set by the eNB, max HARQ num,min HARQ RTT, and min gNB delay may be determined based only on min UEdelay (or max UE delay) (by the UE).

1. For example, it may be set that max HARQ num=min HARQ RTT=L×min UEdelay (or, L×max UE delay), and it may be assumed/applied that min gNBdelay=min UE delay (or max UE delay).

2. L may be predefined to be a specific value (e.g., 2) or configured bythe eNB.

B. Method 1-2: Determination by the Combination of Min UE Delay (or MaxUE Delay) and Min eNB Delay

With min UE delay (and max UE delay) and min eNB delay set by the eNB,max HARQ num and min HARQ RTT may be determined based on the parameters(by the UE). For example, it may be set that max HARQ num=min HARQRTT=min UE delay (or max UE delay)+min gNB delay.

C. Method 1-3: Determination by the Combination of Min UE Delay (or MaxUE Delay) and Max HARQ Num

With min UE delay (and max UE delay) and max HARQ num set by the eNB,min HARQ RTT and min gNB delay may be determined based on the parameters(by the UE).

1. As an example, it may be set that min HARQ RTT=max HARQ num, and mingNB delay=max HARQ num−min UE delay (or max UE delay).

2. For a specific UE type (category) (hereinafter, UE type 1), onlyvalues satisfying max HARQ num≤min UE delay+D may be set. For the otherspecific UE type (category) (hereinafter, UE type 2), only valuessatisfying max HARQ num≥min UE delay+D may be set.

3. D may be D≥1. For example D may be set to 1 (or to the same value asmin eNB delay).

4. UE type 1 may be considered as a UE type in which at least one of themaximum TB size, the total soft buffer size, and the maximum operatingfrequency bandwidth is below a specific level.

D. Method 1-4: Setting Min HARQ RTT to be Equal or Proportional to MaxHARQ Num

The value of one parameter of min HARQ RTT and max HARQ num may be setby the eNB, and the value of the other parameter may be set to be equalto or proportional to the set value. For example, when max HARQ num=N isset by the eNB, min HARQ RTT may also be set to N.

E. Method 1-5: Setting Min HARQ RTT and Max HARQ Num Independently

Min HARQ RTT and max HARQ num may be independently set by the eNB.However, embodiments are not limited thereto. In case of UE type 1, onlyvalues satisfying max HARQ num≤min HARQ RTT may be set. In case of UEtype 2, only values satisfying max HARQ num≥min HARQ RTT may be set.

F. Method 1-6: Setting Min HARQ RTT and Reference Max HARQ NumIndependently

Min HARQ RTT and reference max HARQ num may be independently set by theeNB. However, embodiments are not limited thereto. In case of UE type 1,only values satisfying reference max HARQ num≤min HARQ RTT may be set.the min HARQ RTT, if the UE type 2, In case of UE type 2, only valuessatisfying reference max HARQ num≥min HARQ RTT may be set.

G. Method 1-7: Setting max_N_act and max_N_ref to have the Same Value orDifferent Values

Max_N_act and max_N_ref may be set based on min UE delay and/or max UEdelay and/or min eNB delay (by the UE).

1. As an example, it may be set that max_N_act=max UE delay+min eNBdelay (or, L×max UE delay), and max_N_ref=max UE delay (or min UEdelay)+min eNB delay.

2. As another example, it may be set that max_N_act=min UE delay+min eNBdelay (or, L×min UE delay), and max_N_ref=min UE delay+min eNB delay.

3. L may be predefined to be a specific value (e.g., 2) or configured bythe eNB.

H. Method 1-8: Determination by Min UE Delay (or Max UE Delay) and L

Min HARQ RTT (and min gNB delay) may be determined (by the UE) based onthe value of parameter L and the value of min UE delay (and max UEdelay) set by the eNB.

1. As an example, the UE may determine min HARQ RTT to be min HARQRTT=L×min UE delay (or, L×max UE delay) or min HARQ RTT=min UE delay+L(or, max UE delay+L). The UE may operate on the assumption that min HARQRTT is the minimum scheduling time interval for the same HARQ process.

2. The UE may determine min gNB delay to be min gNB delay=min HARQRTT−min UE delay (or, min HARQ RTT−max UE delay). The UE may operate onthe assumption that min gNB delay is the minimum scheduling time for thesame HARQ process.

3. L may be predefined to be a specific value (e.g., 2, 4) or configuredby the eNB.

I. Method 1-9: Setting a range of possible values of actual max HARQ num

The minimum possible value of actual max HARQ num (max_N_act) may bedetermined by min UE delay, and the maximum possible value may bedetermined by max UE delay (by the UE).

1. As an example, the minimum possible value of max_N_act may bedetermined by (min UE delay+X) and the maximum possible value may bedetermined by (max UE delay+X). Here, X may be configured to be one ofmin gNB delay, parameter L, min UE delay or max UE delay.

2. As another example, only values satisfying (actual) max HARQ num≤minHARQ RTT or (actual) max HARQ num≥min HARQ RTT may be set for any UE(without distinguishing between the UE types).

3. As another example, values satisfying (actual) max HARQ num≤min HARQRTT may be set in the case of dynamic TDD, and (in which DL/ULconfiguration is dynamically changed), and values satisfying (actual)max HARQ num>min HARQ RTT may be set in the case of semi-static DL/ULconfiguration-based TDD or FDD.

(4) HARQ Parameter Setting #2

A. Method 2-1: Assigning a Fixed Buffer Size for Specific DL DataReception

A fixed minimum soft buffer size may be assigned to specific DL datareception (i.e., the minimum number of stored bits per TB may be fixed).

1. Even in the reconfiguration of max HARQ num (correspondingrepartition of the soft buffer), the minimum soft buffer size may not bechanged for specific DL data reception.

2. The specific DL data may have a specific HARQ process ID, bescheduled by a specific DCI format, or be DL data for which a default UEdelay is indicated.

3. The minimum soft buffer size for the specific DL data may be set to asoft buffer size obtained through partition based on the value ofmax_N_ref.

B. Method 2-2: Setting HARQ Parameters Independently for DL and UL

Values of parameter such as UE delay, eNB delay, HARQ RTT, and HARQ nummay be set independently (e.g., to different values) for DL HARQ and ULHARQ.

1. The parameters may include min UE delay, max UE delay, default UEdelay, min eNB delay, default eNB delay, min HARQ RTT, default HARQ RTT,max HARQ num, and default HARQ num.

C. Method 2-3: Report/Configure Min_dUE_Cap and dUE_Default According toSubcarrier Spacing (SCS) and BW

The UE may report a value of min_dUE_cap (e.g., a different value)independently according to the SCS and the operating BW used in the OFDMmodulation/demodulation on the system/cell which the UE accesses. Here,the operating BW includes, for example, the overall system BW(hereinafter, system BW), the maximum operating BW of the UE(hereinafter, max UE BW), or a UE operating BW configured by the eNB(hereinafter, cfg UE BW). The value of dUE_default may also be setdifferently according to the SCS and BW.

1. As an example, the UE may operate to report the value of min_dUE_capfor a specific TB size (e.g., max TB size) based on the system BW,and/or max UE BW, and/or the configured UE BW (and the SCS value of thesystem/cell that the UE accesses). In this case, different values ofmin_dUE_cap may be determined/reported for the same operating BWdepending on the SCS size. Alternatively, different values ofmin_dUE_cap may be determined/reported for the same SCS depending on theoperating BW size.

2. As another example, dUE_default may be set to different values forthe same system BW depending on the SCS size. Alternatively, dUE_defaultmay be set to different values for the same SCS depending on the systemBW size. In this case, the value of dUE_default set based on the systemBW may be applied only to UE type 2, and the value of dUE_default to beapplied to UE type 1 may be set based on max UE BW (and SCS value)having a specific size smaller than the system BW.

D. Method 2-4: Operating the Soft Buffer in the Situation of Operationwith Multiple TTI Lengths

When the HARQ operation is performed based on a plurality of differentTTI lengths, the following soft buffer allocation scheme may beconsidered for each TTI length (by the eNB/UE). For simplicity, a largeTTI length is defined as L-TTI, and the maximum number of HARQ processesconfigured in the L-TTI is defined as N. Also, a small TTI length isdefined as S-TTI and the maximum number of HARQ processes configured inthe S-TTI is defined as M.

1. Opt 1: For each TTI length, a minimum buffer size per TB may beallocated based on the total buffer size. For example, in the case ofL-TTI, the total buffer size may be divided into N sizes and the minimumbuffer size may be allocated per TB. In the case of S-TTI, the totalbuffer size may be divided into M sizes, and the minimum buffer size maybe allocated per TB.

2. Opt 2: The total buffer size may be divided according to the TTIlength, and the minimum buffer size may be allocated per TB based on apartial buffer size allocated to a corresponding one of the TTI lengths.For example, when the total buffer size S is divided at the ratio of A:B(for example, 0<B<A<1, A+B=1), a partial buffer size (A×S) may bedivided into N sizes in case of L-TTI, and a partial buffer size (B×S)may be divided into M sizes in case of S-TTI. Thereby, the minimumbuffer size per TB may be allocated.

3. Opt 3: The minimum buffer size per TB may be allocated based on thetotal buffer size in case of L-TTI and based on a partial buffer size incase of S-TTI. For example, in the case of L-TTI, the total buffer sizeS may be divided into N sizes. In the case of S-TTI, a partial buffersize (B×S) may be divided into M sizes. Thereby, the minimum buffer sizeper TB may be allocated.

4. With buffer dimensioning applied as above, transmission andretransmission over different TTI lengths may be performed on the samedata (e.g., TB). In this case, the minimum buffer size of thecorresponding TB may be allocated as the minimum buffer size per TBconfigured for the TTI length used for initial transmission (notretransmission) of the corresponding TB.

5. Here, the TTI length may be replaced with a duration (e.g., thenumber of symbols) indicated for data transmission with the actual TTIfixed/set to one TTI. For example, the L-TTI may be replaced with a dataduration consisting of a specific number symbols or more symbols, andthe S-TTI may be replaced with a data duration consisting of symbolsfewer than the specific number of symbols.

E. Method 2-5: Reporting Min_Due_Cap According to a Combination ofTBS/BW/SCS/TTI

The UE may operate to report min_dUE_cap thereof to the eNB according toeach combination of (a plurality of) TB sizes (TBS) specificallyconfigured (e.g., predefined for each frequency band), a BW size, an SCSvalue, and TTI length. Further, the eNB may signal to the UE acombination of a specific TBS, a BW size, an SCS value and a TTI lengthby which min_dUE_cap is determined, and the UE may report min_dUE_capthereof to the eNB according to the signaled combination.

F. Method 2-6: Reporting Min_Due_Cap According to DL Control ChannelType and Configuring Candidate HARQ Delay

The UE may report the value of min_dUE_cap to the eNB according to thetype of a DL control channel used for scheduling of a DL/UL shared(data) channel. For example, the UE may independently report the valueof min_due_cap to the eNB depending on whether a DL control channel usedfor scheduling of a DL/UL shared (data) channel is configured in amanner of being subjected to TDM with the DL data channel transmissioninterval while occupying a small number of symbols with a relatively low(maximum) symbol index within one TTI/SF/slot as in the case of theexisting PDCCH of LTE (wherein the TDM scheme has a structure in whichthe control channel is mapped/transmitted ahead of the data channel)(hereinafter, control type 1), or is configured in a manner of beingsubjected to FDM with the DL data channel transmission region whileoccupying a large number of symbols with a relatively high (maximum)symbol index as in the case of the EPDCCH of LTE (hereinafter, controltype 2). (For example, the UE may report different values independentlyfor the respective control types, or report a greater value for controltype 2 than for control type 1).

The types of DL control channels may be distinguished not only by TDM orFDM with the DL data channel transmission interval but also by a gapbetween the last symbol of the control channel and the last symbol of aDL data channel scheduled from the control channel in one TTI/SF/slot(or may be defined by a function for the gap). For example, the value ofthe gap for control type 1 may be greater than that for control type 2.The function for the gap may be defined by a specific equation or table.

Accordingly, a candidate HARQ delay set configured for the UE by the eNBmay also be configured for each DL control channel type independently(for example, differently or so as to have a greater value for controltype 2 than for control type 1). The default UE delay may also be set todifferent values according to the DL control channel types.

Here, the HARQ delay of the data retransmitted from the eNB may besubjected to the following options.

1. Opt 1: Determined according to a control channel type used forinitial transmission scheduling of retransmission data

2. Opt 2: Determined according to a control channel type used forscheduling of the retransmission data

3. Opt 3: Determined to be the greater HARQ delay value between the HARQdelay determined according to the control channel type used for theinitial transmission scheduling of the retransmission data and the HARQdelay determined according to the control channel type used forretransmission scheduling

G. Method 2-7: Report Min_dUE_Cap According to a DL/UL Data SignalMapping Method and Configure Candidate HARQ Delays.

The UE may report the value of min_dUE_cap independently according tohow the DL/UL data signal is mapped, for example, whether the DL/UL datasignal is mapped in a frequency first-time second manner (hereinafter,mapping type 1) as in the case of the existing PDSCH of LTE, or in atime first-frequency second manner (hereinafter, mapping type 2) as inthe case of the PUSCH of LTE. (For example, the UE may report differentvalues or report a greater value in the case of mapping type 1 than inthe case of mapping type 2).

Accordingly, a candidate HARQ delay configured for the UE by the eNB mayalso be set independently for each DL/UL data signal mapping method (forexample, set differently or set such that a greater value is set in thecase of mapping type 2 than in the case of mapping type 1). The defaultUE delay may also be set differently according to the DL/UL data mappingscheme.

H. Method 2-8: Set different default UE delay values applied to UEs thatuse PRACH resources according to the resources

The value of the default UE delay applied to a UE performing/completingthe (initial) random access procedure through use/transmission of aPRACH resource (which may be a form that is distinguished by, forexample, at least one of time, frequency, sequence, and format) may beset differently for each PRACH resource. Such setting may be signaled(broadcast) to the UE via transmission of system information (e.g., SIB)(including PRACH resource configuration information).

Accordingly, the UE selects one of PRACH resources for which dUE_defaultcorresponding to a value greater than or equal to the value ofmin_dUE_cap of the UE is set among a plurality of different dUE_defaultvalues set for different PRACH resources to transmit a PRACH. Thereby,the UE may operate to perform the (initial) random access procedure.

I. Method 2-9: Report Min_Due_Cap and Configure HARQ Delay According toa Timing Offset Set Between Cells/Carriers in a CA Situation

In a situation where CA of a plurality of cells/carriers (collectivelyreferred to as cells) is configured for one UE, a scheduling cell forperforming DL control channel transmission and a scheduled cell forperforming DL/UL data channel transmission scheduled from the DL controlchannel may be configured differently (i.e., cross-carrier schedulingmay be performed), and there may be a (non-zero) timing offset set in anSF/slot/symbol unit that corresponds to a level higher than or equal toa certain level between the two cells. In this case, the UE may reportthe timing offset set information present between the two cells to theeNB, or report the min_dUE_cap information to the eNB based on thetiming offset set information. Thus, a candidate HARQ delay set may beconfigured independently (for example, to have a different value) foreach of a plurality of scheduled cells for which the same schedulingcell is configured, or different candidate HARQ delay sets may beconfigured for a case where the scheduling cell and the scheduled cellemploy the same (UL) timing advance (TA) (i.e., the cells belong to thesame TA group) and a case where the two cells employ different TAs(i.e., the cells belong to different TA groups).

J. Method 2-10: The UE is Caused to Report the Maximum DecodingCapability Thereof or Corresponding Information to the gNB.

The UE may report the maximum decoding capability thereof or informationrelated to a specific (e.g., minimum) HARQ process number Kcorresponding to the maximum decoding capability to the gNB, assumingthat a specific (e.g., nominal) code rate (e.g., 1/2). Thereby, the gNBmay recognize the maximum TB size information about the UE (at thespecific (e.g., nominal) code rate (e.g., 1/2)). Here, the maximumdecoding capability of the UE indicates the maximum number of(decodable)/supportable encoded bits of the UE. In addition, the numberof bits corresponding to the total soft buffer size divided by aspecific (e.g., minimum) HARQ process number K may be the maximum numberof (decodable/supportable) encoded bits of the UE.

[Scheme 2] Minimum HARQ RTT and Soft Buffer Management According to SCS(or TTI Length)

In this scheme, a method for managing the minimum HARQ RTT and softbuffer according to the SCS (a TTI length based thereon) is proposed.

(1) Reference HARQ Parameter Set

First, a HARQ parameter set that is a reference for UE implementation(or a target of UE performance) may be considered as follows.

1) Subcarrier spacing (SCS): K [kHz]

2) TTI length: L [ms]

-   -   N OFDM symbol intervals based on SCS=K [kHz]

3) Maximum aggregated BW: B [MHz] (=M [RBs])

-   -   Maximum reception BW or maximum number of RBs based on SCS=K        [kHz]

4) Maximum TBS (over maximum BW): A [bits]

-   -   Maximum TB size schedulable in L [ms], which is a TTI length    -   When the maximum BW is configured by CA of Nc carriers (with the        same BW), the maximum TBS per carrier may actually be A/Nc        [bits].

5) Minimum HARQ RTT: Y [ms]

-   -   It may be determined according to the minimum HARQ processing        time at the UE (and eNB) (corresponding to the capable min UE        delay of Scheme 1).

6) Reference HARQ process number: Z (=Y/L)

-   -   the maximum number of HARQ processes that are schedulable for Y        [ms], which is a HARQ RTT

7) Total soft buffer size: X [bits]

-   -   the total soft buffer size capable of storing (nominal (or        target or reliable) code rate-based) soft (encoded) bits for the        maximum TBS A [bits] with respect to Z HARQ processes    -   Different UEs may support different values of minimum HARQ RTT Y        [ms], while supporting the same maximum TBS A [bits] and/or the        same total soft buffer size X [bits]

Next, soft buffer dimensioning based will be described on theabove-described reference HARQ parameter set. Soft buffer dimensioningmeans dividing the entire soft buffer into (the minimum) buffer sizesper TB.

1) Minimum buffer size per TB: X/Z [bits]

-   -   Z denotes the maximum value used for soft buffer dimensioning        (hereinafter, the maximum buffer dimensioning value)    -   Even if a HARQ process number greater than Z is set, the minimum        buffer size per TB is limited to X/Z [bits].    -   When the HARQ process number is set to Zs which is less than Z,        the minimum buffer size per TB may be set to X/Zs [bits].    -   When the maximum BW is composed of Nc carriers (with the same        BW), the minimum buffer size per TB for each carrier may be        X/(Z/Nc) [bits].

(2) HARQ Parameters for a Shorter TTI Length

Modified HARQ parameters that may be considered for use in a TTI lengthshorter than the reference SCS-based TTI length (e.g., the normal TTI)are as follows.

1) Common parameters

-   -   SCS: 2K [kHz]    -   TTI length (N OFDM symbols): L/2 [ms]    -   Maximum BW: B [MHz]=M/2 [RBs]    -   Maximum TBS (per TTI): A/2 [bits]    -   Total soft buffer size: X [bits]

2) HARQ parameter set 1

-   -   Minimum HARQ RTT: Y [ms]    -   Reference HARQ process number: 2Z (=Y/(L/2))    -   Minimum buffer size per TB (maximum TBS=A/2): X/(2Z) [bit s]    -   Note: This parameter set is the same as or similar to the        reference parameter set in terms of data (decoding) performance        and signal processing speed.    -   In this case, 2Z is the maximum value used for soft buffer        dimensioning.

3) HARQ parameter set 2

-   -   Minimum HARQ RTT: Y′ [ms] (Y/2≤Y′<Y)    -   Reference HARQ process number: Z′ (Z≤Z′<2Z)    -   Minimum buffer size per TB (maximum TBS=A/2): X/Z′ [bits]        (X/Z′>X/(2Z))    -   Note: This parameter set achieves improved performance (coding)        gain and decrease in latency over the reference parameter set,        while requiring faster signal processing speed (and the maximum        applicable TA is limited to a smaller value).    -   In this case, 2Z is the maximum value used for soft buffer        dimensioning.

Here, by replacing “2” with an arbitrary integer “C” (e.g., replacingthe SCS with C×K [kHz]), the present invention may be generalized to anyshort TTI length.

(3) HARQ Parameters for TTI Length

Modified HARQ parameters that may be considered for use in a TTI lengthlonger than the reference SCS-based TTI length (e.g., the normal TTI)are as follows.

1) Common parameters

-   -   SCS: K/2 [kHz]    -   TTI length (N OFDM symbols): 2L [ms]    -   Maximum BW: B [MHz]=2M [RBs]    -   Maximum TBS (per TTI): 2A [bits]    -   Total soft buffer size: X [bits]

2) HARQ parameter set 1

-   -   Minimum HARQ RTT: Y [ms]    -   Reference HARQ process number: Z/2 (=Y/(2L))    -   Minimum buffer size per TB (maximum TBS=2A): X/(Z/2) [bits]    -   Note: This parameter set is the same as or similar to the        reference parameter set in terms of data (decoding) performance        and signal processing speed.    -   In this case, Z/2 is the maximum value used for soft buffer        dimensioning.

3) HARQ parameter set 2

-   -   Minimum HARQ RTT: Y′ [ms] (Y<Y′≤2Y)    -   Reference HARQ process number: Z′ (Z/2<Z′≤Z)    -   Minimum buffer size per TB (maximum TBS=2A): X/Z′ [bits]        (X/Z′<X/(Z/2))    -   Note: This parameter set is operable at a lower signal        processing speed than the reference parameter set (additionally,        the maximum applicable TA is allowed up to a larger value),        while being degraded in terms of (decoding) performance and        latency reduction.    -   In this case, Z/2 is the maximum value used for soft buffer        dimensioning

Here, by replacing “2” with an arbitrary integer “C” (e.g., replacingthe SCS with K/C [kHz]), the present invention may be generalized to anylonger TTI length.

(4) HARQ Parameter-Related UE Operation

Based on the above configuration, the UE may report, to the eNB, theentirety or a specific part of the HARQ parameter set for each SCS/TTIlength (/frequency band) in a set of a plurality of specific differentSCSs or TTI lengths (or frequency bands). As described above, the HARQparameter set may include, for example, the maximum aggregated BW (ormaximum BW per carrier), the maximum TBS (over the maximum BW or percarrier), the minimum HARQ RTT (with capable UE delay), a reference HARQprocess number, and the maximum buffer dimensioning value.

In the case of a shorter TTI length, a rule may be defined such thatdifferent HARQ parameter sets are implemented according to a (peak) datarate/latency requirement of the UE or a target service application type(e.g., a type among eMBB/URLLC/mMTC). For example, an eMBB (or mMTC)targeting UE may be configured to use HARQ parameter set 1 and a URLLCtargeting UE may be configured to use HARQ parameter set 2 (e.g., theminimum HARQ RTT may be implemented as Y′=Y/C [ms]. Even in the case ofa longer TTI length, a rule may be defined such that different HARQparameter sets are implemented according to a (peak) data rate/latencyrequirement of the UE or a target service application type (e.g., a typeamong eMBB/URLLC/mMTC). For example, an eMBB (or URLLC) targeting UE maybe configured to use HARQ parameter set 1 and a mMTC targeting UE may beconfigured to use HARQ parameter set 2 (e.g., the minimum HARQ RTT maybe implemented as Y′=Y×C [ms]).

In addition, when HARQ parameter set 1/2 in the shorter TTI length isdefined as S-TTI set 1/2 and HARQ parameter set 1/2 in the longer TTIlength is defined as L-TTI set 1/2, the same UE may be specified/limitednot to report (implement/request) the combination of S-TTI set 2 andL-TTI set 2. Given that TTI length 1>TTI length 2>TTI length 3>TTIlength 4, if change from TTI length 1 to TTI length 2 is reported(implemented) with S-TTI set 2 and change from TTI length 2 to TTIlength 3 is reported (implemented) with S-TTI set 1, change from TTIlength 3 to TTI length 4 may be specified/limited to report (implement)only S-TTI set 1 (namely, report (implement/request)S-TTI set 2).Further, given that TTI length 1<TTI length 2<TTI length 3<TTI length 4,if change from TTI length 1 to TTI length 2 is reported (implemented)with L-TTI set 2 and change from TTI length 2 to TTI length 3 isreported (implemented) with L-TTI set 1, change from TTI length 3 to TTIlength 4 may be specified/limited to report (implement) only L-TTI set 1(namely, report (implement/request) L-TTI set 2).

(5) UE Category by (Peak Data Rate, Minimum HARQ RTT, Soft Buffer Size)

It is proposed that the UE category be specified according to acombination of the peak data rate, minimum HARQ RTT, and soft buffersize. The UE category may be understood as a representative value/indexthat represents various kinds of information used in classification ofthe UE category. Accordingly, the UE may deliver various kinds ofinformation used to specify the UE category to the eNB through the UEcategory, and the eNB may use the information obtained through the UEcategory to configure, for the UE, various kinds of information (forexample, see Scheme 1) necessary for HARQ operation.

First, three parameters for specifying a UE category are defined below.

1) Peak data rate (X_(i) Gbps): Maximum number of data (information)bits that can be received in a single slot or TTI

2) Minimum HARQ RTT (Ymin_(i) ms): Minimum interval between(re)transmissions of the same data (e.g., TB) (minimum achievablelatency)

3) Maximum HARQ RTT (Ymax_(i) ms): Maximum time for which the peak ratedata can be continuously received/stored

4) Soft buffer size (Zi bits)=X_(i) [Gbps]×Ymax_(i) [ms]×A

5) ‘A’ may be determined as a function of a specific (e.g., lowest)coding rate R and/or a maximum allowable number of transmissions T(e.g., 4). For example, A may be A=min (1/R, T).

6) R may be determined as the minimum (e.g., mother) coding rate withoutrate-matching or puncturing, or a specific target coding rate higherthan the minimum rate.

7) Ymax_(i) may be greater than or equal to Ymin_(i), depending on UEimplementation. In the following description, Y_(i) (or Y) may be set toYmax_(i) (or Ymin_(i)). In the description above and below, Y_(i) (or Y)may mean Ymax_(i) (or Ymin_(i)).

Based on the definition above, UE category C i may be defined as acombination of (X_(i), Y_(i), Z_(i)). Accordingly, possible UEcategories may be defined in ascending category order as follows.

1) C₁=(X,Y,Z)

A. a UE category defined by a combination of peak rate X and minimum RTTY, and buffer size Z

2) C₂=(X, Y′, Z′), where Y′<Y, and Z′<Z

A. Comparison with C₁

-   -   Support for the same peak rate    -   Support for a smaller minimum latency based on a (faster)        processing capability supporting a smaller minimum RTT    -   Support for a smaller (maximum) HARQ process number for peak        rate data transmission due to a smaller buffer size    -   The buffer size may be determined (reduced) in proportion to the        minimum RTT (e.g., Y′/Y=Z′/Z). For UEs having different        combinations of (minimum RTT, buffer size) and the same ratio        between two parameters (e.g., Y/Z=Y′/Z′) may be        differentiated/defined as different UEs in the UE category        (order).

B. The minimum RTT (or minimum latency) and buffer size which aresupportable for a plurality of UEs supporting the same peak rate may beimplemented differently for each of the UEs, and the minimum RTT andbuffer size may be determined so as to be in proportion to each other.

3) C₃=(X, Y′, Z), where Y′<Y.

A. Comparison with C₁

-   -   Support for the same peak rate    -   Support for smaller minimum latency based on a (faster)        processing capability supporting smaller minimum RTT

Support for the same (maximum) HARQ process number for peak rate datatransmission based on the same buffer size

B. The minimum RTT (or corresponding minimum latency) which aresupportable for a plurality of UEs supporting the same peak rate andbuffer size may be implemented differently for each of the UEs. Inaddition, the buffer size may be differently implemented even for eachof a plurality of UEs supporting the same peak rate and minimum RTT.

4) C₄=(X′, Y′, Z), where X′>X, and Y′<Y.

A. Comparison with C₁

-   -   Support for a higher peak rate    -   Support for a smaller minimum latency based on a (faster)        processing capability supporting a smaller minimum RTT    -   Support for a smaller (maximum) HARQ process number for peak        rate data transmission due to the same buffer size    -   The peak rate may be determined (increased) in proportion to the        maximum supportable BW capability of the UE.    -   The peak rate and the minimum RTT may be determined such that        the product thereof is constant (e.g., X·Y=X′·Y′) while being in        inverse proportion to each other. UEs having different        combinations of (peak rate, minimum RTT) and constant product of        two parameters may be distinguished/defined as different UEs in        the UE category (order).

B. The peak rate and/or minimum RTT (or minimum latency) which aresupportable for a plurality of UEs supporting the same buffer size(and/or minimum RTT) may be implemented differently for each of the UEs.In this case, the peak rate and the minimum RTT may be determined so asto be in inverse proportion to each other

5) C₅=(X′, Y′, Z″), where X X′>X, Y′<Y, and Z″>Z.

A. Comparison with C₁

-   -   Support for a higher peak rate    -   Support for a smaller minimum latency based on a (faster)        processing capability supporting a smaller minimum RTT    -   Support for the same (maximum) HARQ process number for peak rate        data transmission based on a larger buffer size    -   The buffer size may be determined (e.g., increased) in        proportion to the peak rate (e.g., Z″=Z·(X′/X))

B. The buffer size may be implemented differently for each of aplurality of UEs supporting the same peak rate and minimum RTT.

In the description above, the peak (data) rate may refer to aninstantaneous peak rate that can be achieved within a given period oftime with respect to a scheduling unit time (which may be a TTI or slotor subframe, and is referred to as TTI simplicity).

When UEs support the same peak rate, different UE types (e.g.,categories or capabilities) may be considered according to a combinationof the minimum (HARQ) RTT and the (soft) buffer size as follows. Forsimplicity, a buffer size capable of supporting continuous/persistent(peak rate) data reception during one or more TTIs corresponding to theminimum RTT is defined as a “nominal buffer size.”

1) UE types supporting different combinations of (minimum RTT, buffersize) while supporting the same peak rate

A. UE type A: a UE type that supports a soft buffer size larger than thenominal buffer size corresponding to the minimum RTT supported by the UE

B. UE Type B: a UE type that supports the same soft buffer size as thenominal buffer size corresponding to the minimum RTT supported by the UE

C. UE Type C: a UE type that supports a soft buffer size smaller thanthe nominal buffer size corresponding to the minimum RTT supported bythe UE

UE types A/B/C may be implemented so as to support the same minimum RTT(namely may support different buffer sizes) (if they support the samepeak rate). Alternatively, the UE types A/B/C may be implemented so asto support the same buffer size (namely, may support different minimumRTTs) (if they support the same peak rate).

In addition, in the case of UE types A/B/C, a degree of freedom inimplementation may be defined for each UE type according to a data raterequirement, a latency requirement, a duplexing mode, and the like. Asan example, when the required data rate is higher than or equal to aspecific level (e.g., X bps), UE types AB (or all UE types A/B/C) areimplementable. On the other hand, when the required data rate is lowerthan the specific level, a rule may be defined such that implementationis allowed only for UE type (or UE types B/C). As another example, whenthe required latency is lower than or equal to a specific level (e.g., Ymsec), UE types A/B (or UE type B) are implementable. On the other hand,when the required latency exceeds the specific level, a rule may bedefined such that implementation is allowed only for UE type C (or UEtypes B/C). As another example, for a UE that supports TDD operation(when the required data rate is higher than or equal to a specific level(e.g., X bps)), all UE types A/B/C are implementable. On the other hand,for a UE that supports FDD operation, a rule may be defined such thatimplementation is allowed only for UE types A/B.

In the NR system, the (maximum) HARQ process number may be set to aspecific value for the UE by the gNB, and/or may be determined to be adifferent value according to the SCS/TTI or the like. Based on such aconfigurable or variable HARQ process number and a combination of(minimum HARQ RTT, soft buffer size) that is supported by the UE,(actual) HARQ RTT setting and buffer dimensioning may be performed asfollows. For simplicity, the number of TTIs corresponding to the minimumRTT interval is defined as a “nominal HARQ number.” Also, the minimumtime delay (which is set to be greater than or equal to the minimum RTTwhich is the UE capability) between the actual data transmission andretransmission (with the same HARQ process ID) is defined as an actualHARQ RTT.

1) Actual RTT and buffer dimensioning according to a HARQ process numberand a combination of (minimum RTT, buffer size)

A. Actual HARQ RTT: set to the greater one of the nominal HARQ number Xcorresponding to the minimum RTT of the UE and a HARQ process number Y(set by, for example, the gNB)

For example, when Y is set to be greater than X, actual RTT may be setto Y. On the other hand, when Y is set to be less than X, actual RTT maybe set to X.

B. Buffer dimensioning value: set to the smaller one of the nominal HARQnumber X corresponding to the minimum RTT of the UE and a HARQ processnumber Y (set by, for example, the gNB)

-   -   For example, when Y is set to be greater than X, the        dimensioning value may be set to X. On the other end, when Y is        set to be less than X, the dimensioning value may be set to Y.

[Scheme 3] UE Processing Time and HARQ Process Operation

In this scheme, a UE processing time, and corresponding HARQ timing andHARQ process-related operation method are proposed.

(1) UE Processing Time

First, the number of OFDM symbols corresponding to a time intervalbetween a DL data reception (end) time and a corresponding HARQ-ACKtransmission (start) time is defined as DL processing time N1. Thenumber of OFDM symbols corresponding to a time interval between a ULgrant reception (end) time and a corresponding UL data transmission(start) time is defined as UL processing time N2. For simplicity, in thefollowing description, N1 and N2 are denoted by (N1, N2). (N1, N2) mayrepresent N1 and N2 independently or refer to a pair of N1 and N2,depending on the context. That is, (N1, N2) may mean N1, N2 or N1/N2.

(N1, N2) may be set to different values depending on the SCS used fortransmission of DL/UL data (and/or HARQ-ACK or UL grant), a DMRS mappingpattern (symbol position) configured for demodulation of a DL/UL datasignal, an RE mapping method (e.g., a frequency-first or time-firstmanner) for the DL/UL data signal, and/or a ratio of the scheduled DL/ULdata TBS to the peak data rate (i.e., TBS ratio).

For simplicity, the SCS, DMRS pattern, data mapping, TBS ratio, and thelike are defined as (N1, N2)-impacting factors (simply, factors).Multiple candidates for one impacting factor (e.g., [for SCS] X (e.g.,15) kHz and Y (e.g., 30) kHz; [for DMRS pattern] a case where the lastsymbol index including DMRS is X and a case where the last symbol indexis Y; [for data mapping] frequency-first mapping and time-first mapping;[for TBS ratio] X % and Y %, and so on) are defined as factor candidates(simply, candidates).

For candidates (A1, A2) of a specific factor A, (N1, N2) may have thesame value (or be required to have the same value) for all UEs. On theother hand, for candidates (B1, B2) of another factor B, (N1, N2) mayhave different values for the respective UE. In this case, (N1, N2) forcandidates (A1, A2) of factor A may be defined as a single fixed valueand be designated as a mandatory item that all UEs should implement. Onthe other hand, (N1, N2) for candidates (B1, B2) of factor B may bedesignated as a capability item having different values for therespective UEs depending on implementation.

As another example, within the same factor A, (N1, N2) for candidate A1may have the same value (or be required to have the same value) for allUEs, but (N1, N2) for candidate A2 may have different values for therespective UEs depending on the implementation. In this case, within thesame factor A, (N1, N2) for candidate A1 may be defined as a singlefixed value and designated as a mandatory item that all UEs shouldimplement. On the other hand, (N1, N2) for candidate A2 may bedesignated as a capability item that has different values for therespective UEs depending on the implementation.

A data channel/signal and a control channel/signal corresponding to (N1,N2) may be configured to be transmitted on the single CC or on differentCCs (in the CA situation). In this case, different SCSs may beconfigured for the two different channels/signals. For example, in thecase of N1, different SCSs may be used for DL data (e.g., PDSCH) andcorresponding HARQ-ACK (e.g., PUCCH). In the case of N2, different SCSsmay be used for UL grant DCI (e.g., PDCCH) and corresponding UL data(e.g., PUSCH).

Accordingly, when SCS S_d and SCS S_c are used for the datachannel/signal and the control channel/signal, respectively, UEprocessing time (N1, N2) for the data/control combination may bedetermined to be: 1) (N1, N2) given when min (S_d, S_c), which is thevalue of the smaller one of data SCS S_d and control SCS S_c, iscommonly used for data and control; 2) the greater one of (N1, N2) givenwhen S_d is commonly used for data and control and (N1, N2) given whenS_c is commonly used for data and control (in terms of absolute time);or 3) a×N_d+b×N_c, where the value of N given when S_d is commonly usedfor data and control is N_d and the value of N given when S_c iscommonly used for data and control is N_c (wherein a+b=1 and, forexample, a=b=0.5).

UCI (e.g., HARQ-ACK, CSI) may be transmitted on a UL data channel (e.g.,PUSCH), not on a UL control channel (e.g., PUCCH) (after beingmultiplexed with the UL-SCH). To this end, the UE processing times (N1,N2, N3) may be defined as follows.

1) N1: the number of OFDM symbols corresponding to a time intervalbetween a DL data (e.g., PDSCH) reception (end) time and a correspondingHARQ-ACK (e.g., PUCCH) transmission (start) time

2) N2: the number of OFDM symbols corresponding to a time intervalbetween a UL grant (e.g., PDCCH) reception (end) time and acorresponding UL data (e.g., PUSCH) transmission (start) time

3) N3: the number of OFDM symbols corresponding to a time intervalbetween a specific RS (e.g., CSI-RS) reception (end) time and acorresponding CSI feedback (e.g., PUCCH) transmission (start) time

According to the definition above, the UE processing time N4 requiredwhen the UCI is piggybacked and transmitted on PUSCH may be determinedbased on a specific one of a processing time required for UCItransmission (on PUCCH) (Nu=N1 or N3) and a processing time N2 requiredfor PUSCH transmission (without UCI) (e.g., N4=max(Nu, N2)+z), or may bedetermined to be N4=(a×Nu+b×N2)+z. Here, a+b=1, and, for example,a=b=0.5. z may be 0 or a positive integer (e.g., 1). In addition, theprocessing time N4 required when HARQ-ACK and CSI are piggybacked andtransmitted on PUSCH simultaneously may be determined in a similarmanner (e.g., N4=max(N1, N2, N3)+z or N4=(a×N1+b×N2+c×N3)+z). Inaddition, the processing time N5 required when HARQ-ACK and CSI aresimultaneously transmitted on the same PUCCH may be determined in asimilar manner (e.g., N5=max(N1, N3)+z or N5=(a×N1+b×N3)+z).

When different SCSs S_d and S_c are used for the PUSCH and the UCIPUCCH, the processing time N4 when the UCI is piggybacked andtransmitted on the PUSCH may be determined to be: 1) N4 given whenmin(S_d, S_c), which is the similar one of the SCS S_d for the PUSCH andthe SCS S_c for the PUCCH, is commonly used for the PUSCH and PUCCH; 2)the greater one of N4 given when S_d is commonly used for the PUSCH andPUCCH and N4 given when S_c is commonly used for the PUSCH and PUCCH (interms of absolute time); or 3) a×N_d+b×N_c, where the value of N givenwhen S_d is used for the PUSCH and PUCCH is N_d and the value of N givenwhen S_c is used for the PUSCH and PUCCH is N_c (wherein a+b=1 and, forexample, a=b=0.5). In addition, the processing time N4 required whenHARQ-ACK and CSI are piggybacked and transmitted on PUSCH simultaneouslymay be determined in a similar manner, for example, as the minimum SCS,the maximum absolute time, or a combination of processing times,configured for the HARQ-ACK PUCCH, CSI PUCCH and PUSCH. In addition, theprocessing time N5 required when HARQ-ACK and CSI are simultaneouslytransmitted on the same PUCCH may be determined in a similar manner, forexample, as the minimum SCS, the maximum absolute time, or a combinationof processing times, configured for the HARQ-ACK PUCCH and CSI PUCCH.

The (minimum) HARQ timings (K1, K2) applied to the actual slot(index)-based signal transmission may be determined by adding a(propagation) delay and/or timing advance (TA) to the UE processingtimes (N1, N2). In this case, in order to determine (K1, K2), Opt 1) theTA value configured for each UE may be (UE-specifically) applied, or Opt2) The maximum value that the TA may have may be (UE-commonly) applied.

Opt 1 and Opt 2 may be applied differently depending on situations andconditions. For example, Opt 2 may be applied to DL/UL data transmission(e.g., Msg3 PUSCH, Msg4 PDSCH) in the initial access or(contention-based) random access procedure. In this case, the processingtime (N1, N2) may be set to the maximum value among the processing timesthat a UE can support. On the other hand, Opt 1 may be applied to DL/ULdata transmission (e.g. unicast PDSCH/PUSCH) in the other situations(e.g., a situation after RRC connection). In this case, the processingtime (N1, N2) may be set to a UE-specific processing time supported by aspecific UE.

Different values of (K1, K2) may correspond to the respective candidatesof a specific factor, and the HARQ RTT, max HARQ process number, andsoft buffer dimensioning values may be determined based on the greatestvalue (or least value) among the different values of (K1, K2).

(2) HARQ Timing Configuration

A plurality of candidate HARQ timings (a set thereof) having the samevalue or more values based on (K1, K2) may be preconfigured throughhigher layer signaling (e.g., RRC signaling). In this case, the eNB mayinstruct the UE, through DL/UL grant DCI for scheduling DL/UL data, touse one HARQ timing of the plurality of candidate HARQ timings (in theset thereof) to perform actual signal transmission.

Specifically, the HARQ timing set may be configured differently (namely,composed of different HARQ timings) for the respective candidates of thefollowing factors, including factors {SCS, DMRS pattern, data mapping,TBS ratio}. For example, HARQ timings with smaller/greater (delay)values may be configured for a candidate having a smaller/greater valueof (N1, N2) or (K1, K2).

1) PDCCH Duration

A. For example, when the symbol interval length and/or the last symbolposition (index) at which the PDCCH (for UL grant) is transmitted is Xand Y,

B. A plurality of candidate symbol indexes (a set thereof) that may bedesignated as a start symbol on which the PUSCH (scheduled from thecorresponding PDCCH) is mapped/transmitted (scheduled from) may beconfigured differently for each PDCCH duration.

2) PUCCH Format

A. For example, when the first symbol position (index) and/or the symbolinterval length at which the PUCCH (for HARQ-ACK) is transmitted is Xand Y,

B. A plurality of candidate timings (a set thereof) which may bedesignated by a delay value between PDSCH and HARQ-ACK (corresponding toHARQ-ACK transmission on a corresponding PUCCH) may be configureddifferently for each PUCCH format.

Alternatively, only one HARQ timing set may be configured for a specificfactor, different timings applicable in the set may be configured forthe respective candidates of the factor.

For example, for DMRS patterns 1 and 2 in which the index of the lastsymbol with DMRS in an SF/slot is set to X and Y (wherein X<Y),respectively, one HARQ timing set {T1, T2, T3, T4} may be configured(based on DMRS pattern 1 having the smaller value of N1 or K1) (whereinT1<T2<T3<T4). In this situation, for DMRS pattern 1, any timing of {T1,T2, T3, T4} is applicable. On the other hand, for DMRS pattern 2, onlysome specific timings (e.g., T3, T4) (having, for example, a greaterdelay value) may be configure to be applicable.

As another example, for TTIs 1 and 2 in which the maximum data durationor DCI detection period is set to N symbols and L symbols (wherein N>L),respectively, only one HARQ timing set {T1, T2, T3, T4} may beconfigured (based on scheduling TTI 1 having a greater value of N1 orK1) (wherein T1<T2<T3<T4). In this situation, all timing {T1, T2, T3,T4} may be applicable for TTI 1. On the other hand, for TTI 2, only somespecific timings (e.g., T1, T2) (having, for example, a smaller delayvalue) may be configured to be applicable.

As another method, only one HARQ timing set may be configured for aspecific factor, and timings obtained by adding a specific offset valueto the timings constituting the set may be applied for a specificcandidate.

For example, for DMRS patterns 1 and 2 in which the index of the lastsymbol with DMRS in an SF/slot is set to X and Y (wherein X<Y),respectively, one HARQ timing set {T1, T2, T3, T4} may be configured(based on DMRS pattern 1 having the smaller value of N1 or K1) (whereinT1<T2<T3<T4). In this situation, for DMRS pattern 1, {T1, T2, T3, T4} isapplicable. On the other hand, for DMRS pattern 2, {T1+To, T2+To, T3+To,T4+To} obtained by adding a specific offset To (e.g., a positive number)to the original timing set may be applied.

As another example, for TTIs 1 and 2 in which the maximum data durationor DCI detection period is set to N symbols and L symbols (wherein N>L),respectively, only one HARQ timing set {T1, T2, T3, T4} may beconfigured (based on scheduling TTI 1 having a greater value of N1 orK1) (wherein T1<T2<T3<T4). In this situation, all timing {T1, T2, T3,T4} may be applicable for TTI 1. On the other hand, for TTI 2, {T1+To,T2+To, T3+To, T4+To} obtained by adding a specific offset To (e.g., anarrative number) to the original timing set may be applied.

In the case of HARQ-ACK feedback transmission according to DL datareception, a plurality of candidate PUCCH resources/formats (a setthereof) may be preconfigured through higher layer signaling (e.g., RRCsignaling). In this situation, the eNB may instruct the UE, through DLgrant DCI for scheduling DL data, to use one specific PUCCHresource/format belonging to the PUCCH resource/format set for actualHARQ-ACK transmission. Here, the PUCCH resource/format set may beconfigured differently for the respective candidates of the factors(SCS, DMRS pattern, data mapping, TBS ratio, PDCCH interval) used for DLdata transmission/scheduling. As an example, different PUCCH formats maybe configured for the respective candidates of the factors. In addition,a PUCCH format configured with a smaller/larger interval (number ofsymbols) may be configured for a candidate having a smaller/greatervalue of N1 or K1.

(3) Soft Buffer Management

In the NR system, a plurality of CCs based on different RATs (e.g., NR,and LTE) may be configured for one UE in a manner of carrier aggregation(CA) or dual connectivity (DC) to enable multi-carrier operation.

In this situation, if a backhaul link between the RATs is non-ideallydeployed, it may not be easy for the schedulers (e.g., eNB) responsiblefor the respective RATs to be tightly interworked in real time. In thiscase, the entire soft buffer of the UE may be semi-statically split andused for the RATs.

In this case, in order to ensure performance of DL data receptionthrough the CCs belonging to each RAT with the buffer portions for therespective RATs split from the entire soft buffers, a lower limit is setto the minimum buffer size for each CC in each buffer portion.

For example, when the maximum number of CCs that may be set for the UEis K and the total soft buffer size is S, if the buffer size is split ata ratio of RAT1:RAT2=K1:K2 between RAT1 and RAT2, the buffer sizesallocated to the respective RATs and the buffer size allocated to one CCin each RAT may be configured as follows.

1) Buffer size for RAT1: S1=S×(K1/K)

A. Buffer size per CC in RAT1: C1=S1/min{N1, K1}

B. N1 denotes the number of CCs configured/set in RAT1 (by CA).

2) Buffer size for RAT2: S2=S×(K2/K)

A. Buffer size per CC in RAT2: C2=S2/min{N2, K2}

B. N2 denotes the number of CCs configured/set in RAT2 (by CA).

As another method, the entire soft buffer may be dynamically split orshared between the RATs (unlike the semi-static scheme described above).In this case, buffer portions for the respective RATs may be differentlyallocated within the entire buffer according to the difference or ratiobetween the maximum TBSs set for the respective RATs.

For example, when the ratio of the maximum TBSs for RAT1 and RAT2 is setto RAT1:RAT2=A:B (wherein, for example, A=1, B=1, or A+B=2), if N1 CCsand N2 CCs are configured/set for RAT1 and RAT2 (wherein N=N1+N2), thebuffer sizes allocated to the respective RATs may be configured asfollows.

1) Buffer size for RAT1: S1=S×A×(N1/N)

2) Buffer size for RAT2: S2=S×B×(N2/N)

FIG. 22 illustrates transmission of a wireless signal in accordance withthe present invention.

Referring to FIG. 22 , the minimum storage space per data may be checkedin a HARQ buffer (e.g., a soft buffer) based on a TTI length of acommunication device (S2202), and data for transmission of the wirelesssignal may be stored in the HARQ buffer based on the minimum storagespace per data (S2204). Thereafter, the communication device maytransmit the data in the HARQ buffer for a first TTI (S2206). Thecommunication device may be a UE or a BS.

When the data is retransmitted data, the minimum storage space per datamay be based on a length of a second TTI used for initial transmissionof the data, wherein the length of the second TTI may be different fromthe length of the first TTI.

Here, the minimum storage space per data may be checked by dividing thetotal space of the HARQ buffer by the number of HARQ processescorresponding to the TTI length. The minimum storage space per data mayalso be checked by dividing the entire space of the HARQ buffer into aplurality of sub-HARQ buffers according to the number of TTI lengths andthen dividing each of the sub-HARQ buffers by the number of HARQprocesses corresponding to a corresponding TTI length.

In addition, when the length of the first TTI is greater than the lengthof the second TTI, the minimum storage space per data based on thelength of the first TTI may be checked by dividing the entire space ofthe HARQ buffer by the number of HARQ processes corresponding to thelength of the first TTI, and the minimum storage space per data based onthe length of the second TTI may be checked by dividing a partial spaceof the HARQ buffer by the number of HARQ processes corresponding to thelength of the second TTI.

In addition, the communication device may have a plurality of CCs fordifferent RATs aggregated, and the size of the HARQ buffer may bedetermined by the following equations according to the RATs used fortransmission of the wireless signal:

-   -   Buffer size for RAT1: S*A*(N1/N)    -   Buffer size for RAT2: S*B*(N2/N)

Here, S denotes the total HARQ buffer size in the communication device,and A and B denote coefficients indicative of a ratio of the buffersizes for RAT1 and RAT2. N1 denotes the number of CCs configured forRAT1, N2 denotes the number of CCs configured for RAT2, and N denotesthe sum of N1 and N2.

In addition, a size of the TTI length may be given in the followingorder according to the service type: URLLC<eMBB<mMTC. In addition, thewireless communication system may include a 3GPP LTE-based wirelesscommunication system, and the TTI length may be a multiple of a subframeor slot.

FIG. 23 illustrates a BS and a UE of a wireless communication system,which are applicable to embodiments of the present invention.

Referring to FIG. 23 , the wireless communication system includes a BS110 and a UE 120. When the wireless communication system includes arelay, the BS or UE may be replaced by the relay.

The BS 110 includes a processor 112, a memory 114 and a radio frequency(RF) unit 116. The processor 112 may be configured to implement theprocedures and/or methods proposed by the present invention. The memory114 is connected to the processor 112 and stores information related tooperations of the processor 112. The RF unit 116 is connected to theprocessor 112 and transmits and/or receives an RF signal. The UE 120includes a processor 122, a memory 124 and an RF unit 126. The processor122 may be configured to implement the procedures and/or methodsproposed by the present invention. The memory 124 is connected to theprocessor 122 and stores information related to operations of theprocessor 122. The RF unit 126 is connected to the processor 122 andtransmits and/or receives an RF signal.

The embodiments of the present invention described hereinbelow arecombinations of elements and features of the present invention. Theelements or features may be considered selective unless otherwisementioned. Each element or feature may be practiced without beingcombined with other elements or features. Further, an embodiment of thepresent invention may be constructed by combining parts of the elementsand/or features. Operation orders described in embodiments of thepresent invention may be rearranged. Some constructions of any oneembodiment may be included in another embodiment and may be replacedwith corresponding constructions of another embodiment. It will beobvious to those skilled in the art that claims that are not explicitlycited in each other in the appended claims may be presented incombination as an embodiment of the present invention or included as anew claim by a subsequent amendment after the application is filed.

In the embodiments of the present invention, a description is madecentering on a data transmission and reception relationship among a BS,a relay, and an MS. In some cases, a specific operation described asperformed by the BS may be performed by an upper node of the BS. Namely,it is apparent that, in a network comprised of a plurality of networknodes including a BS, various operations performed for communicationwith an MS may be performed by the BS, or network nodes other than theBS. The term ‘BS’ may be replaced with the term ‘fixed station’, ‘NodeB’, ‘enhanced Node B (eNode B or eNB)’, ‘access point’, etc. The term‘UE’ may be replaced with the term ‘Mobile Station (MS)’, ‘MobileSubscriber Station (MSS)’, ‘mobile terminal’, etc.

The embodiments of the present invention may be achieved by variousmeans, for example, hardware, firmware, software, or a combinationthereof. In a hardware configuration, the methods according to theembodiments of the present invention may be achieved by one or moreApplication Specific Integrated Circuits (ASICs), Digital SignalProcessors (DSPs), Digital Signal Processing Devices (DSPDs),Programmable Logic Devices (PLDs), Field Programmable Gate Arrays(FPGAs), processors, controllers, microcontrollers, microprocessors,etc.

In a firmware or software configuration, the embodiments of the presentinvention may be implemented in the form of a module, a procedure, afunction, etc. For example, software code may be stored in a memory unitand executed by a processor. The memory unit is located at the interioror exterior of the processor and may transmit and receive data to andfrom the processor via various known means.

Those skilled in the art will appreciate that the present invention maybe carried out in other specific ways than those set forth hereinwithout departing from the spirit and essential characteristics of thepresent invention. The above embodiments are therefore to be construedin all aspects as illustrative and not restrictive. The scope of theinvention should be determined by the appended claims and their legalequivalents, not by the above description, and all changes coming withinthe meaning and equivalency range of the appended claims are intended tobe embraced therein.

The present invention is applicable to UEs, eNBs or other apparatuses ofa wireless mobile communication system.

What is claimed is:
 1. A method for transmitting a signal by a UserEquipment (UE) in a wireless communication system, the methodcomprising: transmitting, to a network, a UE capability informationrelated to an uplink processing time; receiving, from the network, aPhysical Downlink Control Channel (PDCCH) based on a first SubcarrierSpacing (SCS); and based on the uplink processing time being elapsedfrom an ending time of the PDCCH, transmitting, to the network, aPhysical Uplink Shared Channel (PUSCH), scheduled by the PDCCH, based ona second SCS, wherein the uplink processing time is determined to alarger one among a first processing time and a second processing time,wherein the first processing time is determined based on a number ofsymbols for the first SCS, and the second processing time is determinedbased on a number of symbols for the second SCS, and wherein the firstprocessing time and the second processing time are determined based onthe UE capability information.
 2. The method of claim 1, wherein theprocessing time is a time required for the UE to process the PDCCH andto prepare the PUSCH.
 3. The method of claim 1, wherein the symbolsincludes Orthogonal Frequency Division Multiplexing (OFDM)-basedsymbols.
 4. The method of claim 1, wherein a Timing Advance (TA) valueis applied to the transmission of the PUSCH.
 5. The method of claim 1,wherein, before the processing time for the PDCCH is elapsed from theending time of the PDCCH, the PUSCH is not transmitted.
 6. A UserEquipment (UE) configured to operate in a wireless communication system,the UE comprising: at least one Radio Frequency (RF) units; at least oneprocessor; and at least one computer memory operably connectable to theat least one processor and storing instructions that, when executed bythe at least one processor, perform operations comprising: transmitting,to a network, a UE capability information on an uplink processing time;receiving, from the network, a Physical Downlink Control Channel (PDCCH)based on a first Subcarrier Spacing (SCS); and based on the uplinkprocessing time being elapsed from an ending time of the PDCCH,transmitting, to the network, a Physical Uplink Shared Channel (PUSCH),scheduled by the PDCCH, based on a second SCS, wherein the uplinkprocessing time is determined to a larger one among a first processingtime and a second processing time, and wherein the first processing timeis determined based on a number of symbols for the first SCS, and thesecond processing time is determined based on a number of symbols forthe second SCS.
 7. The UE of claim 6, wherein the processing time is atime required for the UE to process the PDCCH and to prepare the PUSCH.8. The UE of claim 6, wherein the symbols includes Orthogonal FrequencyDivision Multiplexing (OFDM)-based symbols.
 9. The UE of claim 6,wherein a Timing Advance (TA) value is applied to the transmission ofthe PUSCH.
 10. The UE of claim 6, wherein, before the processing timefor the PDCCH is elapsed from the ending time of the PDCCH, the PUSCH isnot transmitted.
 11. A communication device configured to operate in awireless communication system, the communication device comprising: atleast one processor; and at least one computer memory operablyconnectable to the at least one processor and storing instructions that,when executed by the at least one processor, perform operationscomprising: transmitting, to a network, a UE capability informationrelated to an uplink processing time; receiving, from the network, aPhysical Downlink Control Channel (PDCCH) based on a first SubcarrierSpacing (SCS); and based on the uplink processing time being elapsedfrom an ending time of the PDCCH, transmitting, to the network, aPhysical Uplink Shared Channel (PUSCH), scheduled by the PDCCH, based ona second SCS, wherein the uplink processing time is determined to alarger one among a first processing time and a second processing time,and wherein the first processing time is determined based on a number ofsymbols for the first SCS, and the second processing time is determinedbased on a number of symbols for the second SCS, and wherein the firstprocessing time and the second processing time are determined based onthe UE capability information.
 12. The communication device of claim 11,wherein the processing time is a time required for the communicationdevice to process the PDCCH and to prepare the PUSCH.
 13. Thecommunication device of claim 11, wherein the symbols includesOrthogonal Frequency Division Multiplexing (OFDM)-based symbols.
 14. Thecommunication device of claim 11, wherein a Timing Advance (TA) value isapplied to the transmission of the PUSCH.
 15. The communication deviceof claim 11, wherein, before the processing time for the PDCCH iselapsed from the ending time of the PDCCH, the PUSCH is not transmitted.